Catheter having unirail pullwire architecture

ABSTRACT

A steerable catheter comprises a flexible catheter body including a proximal shaft section and a distal articulating section, a proximal steering interface coupled to the proximal shaft section, and at least one hollow stiffening member extending through the proximal shaft section. The stiffening member(s) is more rigid than the proximal shaft section and is laterally offset from a geometric cross-sectional center of the proximal shaft section. The steerable catheter further comprises circumferentially spaced lumens extending through the distal articulating section, and pullwires extending through the stiffening member(s) in the proximal shaft section and the respective lumens in the distal articulating section. Each of the pullwires has a distal end that terminates in the catheter body distal to the distal articulating section and a proximal end that terminates in the steering interface. The steering interface is manipulatable to selectively tension the pullwires to bend the distal articulating section.

FIELD OF INVENTION

The invention relates generally to minimally-invasive instruments andsystems, such as manually or robotically steerable catheter systems, andmore particularly to steerable catheter systems for performing minimallyinvasive diagnostic and therapeutic procedures.

BACKGROUND

Minimally invasive procedures are preferred over conventional techniqueswherein the patient's body cavity is open to permit the surgeon's handsaccess to internal organs. Thus, there is a need for a highlycontrollable yet minimally sized system to facilitate imaging,diagnosis, and treatment of tissues which may lie deep within a patient,and which may be accessed via naturally-occurring pathways, such asblood vessels, other lumens, via surgically-created wounds of minimizedsize, or combinations thereof.

Currently known minimally invasive procedures for the treatment ofcardiac, vascular, and other disease conditions use manually orrobotically actuated instruments, which may be inserted transcutaneouslyinto body spaces such as the thorax or peritoneum, transcutaneously orpercutaneously into lumens such as the blood vessels, through naturalorifices and/or lumens such as the mouth and/or upper gastrointestinaltract, etc. Manually and robotically-navigated interventional systemsand devices, such as steerable catheters, are well suited for performinga variety of minimally invasive procedures. Manually-navigated cathetersgenerally have one or more handles extending from their proximal endwith which the operator may steer the pertinent instrument.Robotically-navigated catheters may have a proximal interface configuredto interface with a catheter driver comprising, for example, one or moremotors configured to induce navigation of the catheter in response tocomputer-based automation commands input by the operator at a masterinput device in the form of a work station.

In the field of electrophysiology, robotic catheter navigation systems,such as the Sensei® Robotic Catheter System (manufactured by HansenMedical, Inc.), have helped clinicians gain more catheter control thataccurately translates the clinician's hand motions at the workstation tothe catheter inside the patient's heart, reduce overall procedures(which can last up to four hours), and reduce radiation exposure due tofluoroscopic imaging necessary to observe the catheter relative to thepatient anatomy, and in the case of electrophysiology, within therelevant chamber in the heart. The Sensei® Robotic Catheter Systememploys a steerable outer catheter and a steerable innerelectrophysiology (EP) catheter, which can be manually introduced intothe patient's heart in a conventional manner. The outer and innercatheters are arranged in an “over the wire” telescoping arrangementthat work together to advance through the tortuous anatomy of thepatient. The outer catheter, often referred to as a guiding sheath,provides a steerable pathway for the inner catheter. Proximal adapterson the outer guide sheath and inner EP catheter can then be connected tothe catheter driver, after which the distal ends of the outer sheath andinner EP catheter can be robotically manipulated in the heart chamberwithin six degrees of freedom (axial, roll, and pitch for each) viaoperation of the Sensei® Robotic Catheter System.

While the Sensei® Robotic Catheter System is quite useful in performingrobotic manipulations at the operational site of the patient, it isdesirable to employ robotic catheter systems capable of allowing aphysician to access various target sites within the human vascularsystem. In contrast to the Sensei® Robotic Catheter System, which isdesigned to perform robotic manipulations within open space (i.e.,within a chamber of the heart) after the outer guide sheath and innercatheter are manually delivered into the heart via a relativelynon-tortuous anatomical route (e.g., via the vena cava), and thereforemay be used in conjunction with sheaths and catheters that are bothaxially and laterally rigid, robotic catheter systems designed tofacilitate access to the desired target sites in the human vascularsystem require simultaneous articulation of the distal tip withcontinued insertion or retraction of an outer guide sheath and an innercatheter. As such, the outer guide sheath and inner catheter should belaterally flexible, but axially rigid to resist the high axial loadsbeing applied to articulate the outer guide sheath or inner catheter, inorder to track through the tortuous anatomy of the patient. In thisscenario, the inner catheter, sometimes called the leader catheterextends beyond the outer sheath and is used to control and bend a guidewire that runs all the way through the leader catheter in anover-the-wire configuration. The inner catheter also works inconjunction with the outer guide sheath and guide wire in a telescopingmotion to inchworm the catheter system through the tortuous anatomy.Once the guide wire has been positioned beyond the target anatomicallocation, the leader catheter is usually removed so that a therapeuticdevice can be passed through the steerable sheath and manually operated.

Increasing the lateral flexibility of the sheath and catheter, however,introduces catheter navigation problems that may not otherwise occurwhen the sheath and catheter are laterally stiff. For example, manysteerable catheters available today rely on the capability of the userto articulate the distal end of the catheter to a desired anatomicaltarget. The predominant method for articulating the distal end of acatheter is to circumferentially space a multitude of free floatingpullwires (e.g., four pullwires) into the wall of the catheter andattach them to a control ring embedded in the distal end of thecatheter. The anchoring of each pullwire to the control ring is usuallyperformed by soldering, welding, brazing, or gluing the pullwire to thecontrol ring. If four pullwires are provided, the pullwires may beorthogonally spaced from each other. Each of these pullwires are offsetfrom the center line of the catheter, and so when the wires aretensioned to steer the catheter tip, the resulting compressive forcescause the distal tip of the catheter to articulate in the direction ofthe pullwire that is tensioned. However, the compressive forces on therelatively flexible catheter shaft also cause undesired effects.

For example, the axial compression on the catheter shaft during asteering maneuver that bends the distal end of the catheter may causeundesired lateral deflection in the catheter shaft, thereby renderingthe catheter mechanically unstable.

As another example, the curvature of the catheter shaft may make thearticulation performance of the catheter unrepeatable and inconsistent.In particular, because the pullwires are offset from the neutral axis ofthe catheter shaft, bending the catheter shaft will tighten thepullwires on the outside of the curve, while slackening the pullwires onthe inside of the curve. As a result, the amount of tension that shouldbe applied to the pullwires in order to effect the desired articulationof the catheter distal end will vary in accordance with the amount ofcurvature that is already applied to the catheter.

As still another example, when bent, the articulate catheter distal endwill tend to curve align with the catheter shaft. In particular, asshown in FIGS. 1A and 1B, operating or tensioning a pullwire on theoutside edge of a bend may cause the catheter to rotate or twist as thepullwire may tend to rotate the distal articulating section of thecatheter until the pullwire is at the inside edge of the bend. Thisrotation or twist phenomenon or occurrence is known as curve alignment.

That is, when the proximal shaft section of the catheter is curved (asit tracked through curved anatomy), and the distal section is requiredto be articulated in a direction that is not aligned with the curvaturein the shaft, a wire on the outside of the bend is pulled, as shown inFIG. 1A. A torsional load (T) is applied to shaft as tension increaseson the pull-wire on the outside of the bend. This torsional load rotatesthe shaft until the wire being pulled is on the inside of the bend, asshown in FIG. 1B. In effect, the tensioned wire on the outside of thebend will take the path of least resistance, which may often be torotate the shaft to the inside of the bend rather than articulate thetip of the catheter adequately.

This un-intentional rotation of the shaft causes instability of thecatheter tip and prevents the physician from being able to articulatethe catheter tip in the direction shown in FIG. 1A. That is, no matterwhich direction the catheter tip is intended to be bent, it willultimately bend in the direction of the proximal curve. The phenomenonis known as curve alignment because the wire that is under tension isputting a compressive force on both the proximal and distal sections andso both the proximal and distal curvature will attempt to align in orderto achieve lowest energy state. The operator may attempt to roll theentire catheter from the proximal end in order to place the articulateddistal tip in the desired direction. However, this will placed thetensioned inside pullwire to the outside of the proximal bend causingfurther tensioning of the pullwire, and possibly causing the distal endof the catheter to whip around.

All of these mechanical challenges contribute to the instability andpoor control of the catheter tip, as well as increased catheter trackingforces. Some steerable catheters overcome these problems by increasingthe axial stiffness of the entire catheter shaft (e.g., by varying wallthickness, material durometer, or changing braid configuration) oralternatively by incorporating axially stiff members within the cathetershaft to take the axial load. But these changes will also laterallystiffen the catheter shaft, thereby causing further difficulties intracking the catheter through the vasculature of the patient. Therefore,the catheter designer is faced with having to make a compromise betweenarticulation performance and shaft tracking performance. Other steerablecatheters overcome this problem by using free floating coil pipes in thewall of the catheter to respectively housing the pullwires (as describedin U.S. patent application Ser. No. 13/173,994, entitled “SteerableCatheter”, which is expressly incorporated herein by reference), therebyisolating the articulation loads from the catheter shaft. However, theuse of coil pipes adds to the cost of the catheter and takes up morespace in the result, resulting in a thicker catheter wall. Furthermore,because the relatively stiff coil pipes are spaced away from the neutralaxis of the catheter, its lateral stiffness may be unduly increased.

There, thus remains a need to provide a different means for minimizingthe above-described mechanical challenges in a laterally flexible, butaxially rigid, catheter.

Furthermore, although a single region of articulation is typicallysufficient to allow a user to track and steer the catheter though thevasculature, it is sometimes inadequate for tortuous anatomies,navigation of larger vessels, or for providing stability during therapydeployment.

For example, it may be desirable to access either the right coronaryartery or the left coronary artery from the aorta of the patient inorder to remove a stenosis in the artery by, e.g., atherectomy,angioplasty, or drug delivery. The proximal curve of a catheter may bepre-shaped in a manner that locates the distal end of the catheter in anoptimal orientation to access the ostium of the right coronary arteryvia the aorta, as shown in FIG. 2A. However, in the case where it isdesirable to access the ostium of the left coronary artery, the proximalcurve of the catheter locates the distal end of the catheter too farfrom the left coronary artery, which therefore cannot be easily accessedvia manipulation of the distal end of the catheter, as shown in FIG. 2B.Alternatively, the proximal curve of a catheter may be pre-shaped in amanner that locates the distal end of the catheter in an optimalorientation to access the ostium of the left coronary artery via theaorta, as shown in FIG. 2C. However, in the case where it is desirableto access the ostium of the left coronary artery, the proximal curve ofthe catheter locates the distal end of the catheter too close to theright coronary artery, such that the distal end would be seated toodeeply within the ostium of the right coronary artery, as shown in FIG.2D. Thus, it can be appreciated that multiple catheters may have to beused to treat both the left coronary artery and right coronary artery,thereby increasing the cost and time for the procedure.

To complicate matters even further, the articulating distal end of thecatheter needs to be long enough to cross the aorta from the patientright side to the left coronary artery. However, there are varyinganatomies in the population with respect to the positioning of the leftcoronary artery in the aorta. For example, FIG. 3A illustrates theproximal curve required for a catheter to place the distal end withinthe ostium of the left coronary artery in a “normal” anatomy; FIG. 3Billustrates the proximal curve required for a catheter to place thedistal end within the ostium of the left coronary artery in a “wide”anatomy; and FIG. 3C illustrates the proximal curve required for acatheter to place the distal end within the ostium of the left coronaryartery in an “unfolded” anatomy. It can be appreciated that, even if isdesired to only treat the left coronary artery, the clinician may haveto be supplied with multiple catheters, one of which can only be usedfor the particular anatomy of the patient.

One way to address this problem in conventional catheters is to havemultiple unique or independent regions of articulation in the cathetershaft by, e.g., adding a control ring and a set of pullwires for eacharticulation region. Thus, both a proximal region and a distal region ofthe catheter can be articulated. When manufacturing a catheter withinonly a single region of articulation, this task is not overly complex,typically requiring a single lamination of a polymer extrusion to forman outer jacket over an inner polymer tube (or liner) and theinstallation of the control ring with associated pullwires onto theassembly. A braided material can be installed between the inner polymertube and outer polymer jacket to provide select region of the catheterwith increased rigidity.

However, when manufacturing a catheter that has two regions ofarticulation, this task can be difficult and usually requires thelamination of an outer polymer jacket extrusion up to the proximalarticulation region, then the installation of the most proximal controlring with attached pullwires, and then the lamination of an outerpolymer jacket for the remaining portion of the catheter. For catheterswith more than two regions of articulation, this process would have tobe repeated for each and every additional region of articulation.Another issue with respect to the use of control rings is that thelaminated polymer extrusion or extrusions need to be carefully sized atthe control ring, since the ring itself consumes volume in the wall thatnot only requires thinner extrusions so as to not have a bulge in thecatheter at the control ring, but also creates a significantly stifferregion the length of the control ring, which causes a “knuckle” wherethere should be a gradual stiffness change required to achieve goodcatheter performance during tracking through the vasculature.

There, thus, remains a need to provide a more efficient means foranchoring the distal ends of the pullwires at the articulating region orregions of a catheter.

As briefly mentioned above, the inner catheter and guide wire may bearranged in an “over-the-wire” configuration. However, such aconfiguration requires the guide wire to be at least twice as long asthe inner catheter in order to allow the user to continuously hold theguide wire in place as the inner catheter is removed from the outerguide sheath. For example, the inner catheter can have a length up to160 cm, with 140 cm of the catheter being inside the patient. Therefore,to ensure that the position of the guide wire is maintained, thephysician will typically require a guide wire to be over 300 cm long.However, guide wires longer than 300 cm are not readily available insterile catheter laboratories. Additionally, long guide wires require anextra assistant at the bedside to manage the guide wire and ensure itremains in a fixed position and always remains sterile. Furthermore,such a configuration disadvantageously increases the length of the robotrequired to axially displace the guide wire within the inner catheter tothe fullest extent. The increased size of the robot may be impracticaland too big and heavy to be mounted on a table in a catheter labenvironment. Additionally, because the inner catheter passes entirely“over-the-wire,” the inner catheter cannot be robotically removed whileholding the guide wire in place. Instead, the physician needs to removethe guide wire from the robot, and then slide the inner catheterproximally while holding the position of the guide wire fixed. Theprocedure time for removing the inner catheter from the outer guidesheath is increased for an over-the wire configuration (typicallygreater than one minute), thereby increasing fluoroscopic time andradiation exposure to the physician and staff.

A “rapid exchange” leader catheter would alleviate these concerns. Rapidexchange catheter designs have been described and documented in balloonangioplasty catheters, filters, and stent delivery system applications.These designs provide a rapid exchange port on the distal portion of thecatheter shaft, which allows the guide wire to exit and run parallel tothe proximal portion of the catheter shaft. However, no known designsexist for rapid exchange steerable catheters due to the challenge ofnavigating the pullwires proximal of the exit port. In addition, noknown designs exist for the robotic interface for rapid exchangecatheters.

There, thus, remains a need to provide the inner steerable catheter of atelescoping catheter assembly with a rapid exchange architecture.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present inventions, a steerablecatheter comprises a flexible catheter body including a proximal shaftsection and a distal articulating section, and a proximal steeringinterface coupled to the proximal shaft section. The cross-sectionalshape of the catheter body may be any suitable shape, such as circularor rectangular. The steerable catheter further comprises at least onehollow axially stiffening member extending through the proximal shaftsection. The stiffening member(s) is more rigid than the proximal shaftsection and is laterally offset from a geometric cross-sectional centerof the proximal shaft section. In an optional embodiment, the steerablecatheter further comprises a guidewire lumen extending through thedistal articulating section, and a rapid exchange port in communicationwith the guidewire lumen. The rapid exchange port is distal to theproximal shaft section. The stiffening member(s) may form the proximalshaft section.

The steerable catheter further comprises a plurality ofcircumferentially spaced (e.g., equally spaced) lumens extending throughthe distal articulating section. Each of the plurality of lumens may bean unsupported lumen. The steerable catheter further comprises aplurality of pullwires (e.g., three or more) extending through thehollow stiffening member(s) in the proximal shaft section and therespective lumens in the distal articulating section. Each of thepullwires has a distal end that terminates in the catheter body distalto the distal articulating section and a proximal end that terminates inthe proximal steering interface. The steerable catheter may furthercomprise a control ring disposed within the catheter body distal to thedistal articulating section, in which case, the plurality of pullwiresmay be connected to the control ring. The proximal steering interface ismanipulatable to selectively tension the plurality of pullwires to bendthe distal articulating section.

In one embodiment, the stiffening member(s) comprises a singlestiffening member through which the plurality of pullwires extend. Inanother embodiment, the stiffening member(s) comprises a plurality ofstiffening members through which the plurality of pullwires respectivelyextend. In this case, the plurality of stiffening members may be groupedin a manner that locates the centers of the stiffening members within anarcuate angle relative to the geometric cross-sectional center of theproximal shaft section of less than one hundred eighty degrees,preferably less than ninety degrees, and more preferably less thanforty-five degrees.

In another embodiment, the catheter body has a neutral axis, and each ofthe pullwires is located relative to the neutral axis in the proximalshaft section a first distance, and located relative to the neutral axisin the distal articulating section a second distance, thereby definingthe extent to which each of the proximal shaft section and the distalarticulating section articulates when each pullwire is tensioned. Thefirst distance may be greater than the first distance, such that thedistal articulating section articulates independent of the relativebending stiffness between the proximal shaft section and the distalarticulating section when each pullwire is tensioned. The proximal shaftsection may have a first bending stiffness, and the distal articulatingsection may have a second bending stiffness, thereby further definingthe extent to which each of the proximal shaft section and the distalarticulating section articulates when each pullwire is tensioned. Thesecond distance may be greater than the first distance, and the firstbending stiffness may be greater than the second bending stiffness.

In an optional embodiment, the catheter body includes a transitionsection between the proximal shaft section and the distal articulatingsection that transitions the plurality of lumens to the stiffeningtube(s). The transition body section may be more rigid than the distalarticulating section, such that when any of the plurality of pullwiresis selectively tensioned, a resulting compressive force on the catheterbody causes the distal articulating section to bend relative to thetransition section. In one embodiment, the transition section mayinclude spiraled lumens that transition one or more of the plurality oflumens to the stiffening tube(s). In another embodiment, the steerablecatheter may comprise an adapter mounted within the transition section.The adapter has a distal end that interfaces with the plurality oflumens, and a proximal end that interfaces with the stiffening tube(s).The adapter further has a plurality of channels formed in an externalsurface of the adapter. The channel(s) may be spiraled around theexternal surface of the adapter. The plurality of pullwires is disposedwith the respective plurality of channels. If the stiffening member(s)has a single stiffening member through which the plurality of pullwiresextend, the distal end of the adapter may have a plurality of lumens inrespective communication with the plurality of lumens in the distalarticulating section. In this case, the proximal end of the adapter hasa single port in communication with the stiffening tube, and theplurality of pullwires respectively extend through the plurality oflumens of the adapter, along the channels formed in the external surfaceof the adapter, and into the single port of the adapter.

In another optional embodiment, the catheter body includes a proximalarticulating section between the proximal shaft section and thetransition section. The lumens are equally circumferentially spaced fromeach other, such that when all of the pullwires are uniformly tensioned,the resulting compressive force on the catheter body causes the proximalarticulating section to bend relative to the proximal shaft sectionwithout bending the distal articulating section relative to thetransition section. The proximal articulating section may be more rigidthan the distal articulating section, such that when only one of thepullwires is tensioned, the resulting compressive force on the catheterbody causes the distal articulating section to bend relative to thetransition section more than the proximal articulating section bendsrelative to the proximal shaft section.

The steerable catheter may further comprise a lumen extending throughthe proximal articulating section, and a counteracting pullwireextending through the lumen in the proximal articulating section. Thecounteracting pullwire may have a distal end terminating in thetransition section and a proximal end that terminates in the proximalsteering interface, in which case, the proximal steering interface mayfurther be manipulatable to tension the counteracting pullwire toprovide a compressive force on the catheter body that opposes thecompressive force provided by the plurality of pullwires when tensioned.The counteracting pullwire may be circumferentially disposed 180 degreesfrom a common mode of the plurality of pullwires in the proximalarticulating section. The steerable catheter may further compriseanother lumen extending through the proximal articulating section, andanother counteracting pullwire extending through the other lumen in theproximal articulating section. The other counteracting pullwire has adistal end terminating in the transition section and a proximal end thatterminates in the proximal steering interface. In this case, theproximal steering interface may be further manipulatable to tension theother counteracting pullwire to provide a compressive force on thecatheter body that opposes the compressive force provided by theplurality of pullwires when tensioned. The counteracting pullwires maybe respectively circumferentially disposed 120 degrees and 240 degreesfrom a common mode of the plurality of pullwires in the proximalarticulating section.

In accordance with another aspect of the present inventions, arobotically controlled catheter system comprises the previouslydescribed steerable catheter, a drive assembly coupled to the proximalsteering interface of the steerable catheter, and a master controllerincluding a user interface configured for being manipulated to actuatethe drive assembly, thereby selectively tensioning the plurality ofpullwires to bend the distal articulating section. The roboticallycontrolled catheter system may further comprise a processor configuredfor receiving an input from the user interface defining a distalarticulation angle and a distal articulation roll of the distalarticulating section of the steerable catheter, and determining which ofthe pullwires to be displaced and the respective distances that thepullwires should be displaced to achieve the defined distal articulationangle and distal articulation roll of the distal articulating section ofthe steering catheter.

In accordance with still another aspect of the present inventions, arobotically controlled catheter system comprises the previouslydescribed steerable catheter, a drive assembly coupled to the proximalsteering interface of the steerable catheter, a master controllerincluding a user interface configured for being manipulated to actuatethe drive assembly, thereby selectively tensioning the plurality ofpullwires and the counteracting pullwire, and a processor configured forreceiving an input from the user interface defining a distalarticulation angle and a distal articulation roll of the distalarticulating section of the steering catheter, and further defining aproximal articulation angle of the proximal articulating section,determining which of the pullwires to be displaced and the respectivedistances that the pullwires should be displaced to achieve the defineddistal articulation angle and distal articulation roll of the distalbody section of the steering catheter, predicting a proximalarticulation angle of the proximal articulating section solely caused bya moment applied to the distal articulating section and a moment appliedto the transition section by the displacement of the pullwires,computing a difference between the predicted proximal articulation angleand the defined proximal articulation angle to obtain a correctedproximal articulation angle, and determining an additional distance thatat least one of the plurality of pullwires and the counteractingpullwire should be displaced to further achieve the corrected proximalarticulation angle.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of various embodiments ofthe present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIGS. 1A and 1B are plan views showing a curve alignment phenomenon thatmay occur when articulating a prior art steerable catheter;

FIGS. 2A-2D are plan views showing possible issues related to using aprior art catheter having a single region of articulation for accessingboth the left coronary artery and a right coronary artery of a patient'sanatomy;

FIGS. 3A-3C are plan views showing possible issues related to using aprior art catheter having a single region of articulation for accessingdifferent left coronary artery anatomies;

FIG. 4 is a perspective view of a medical robotic system constructed inaccordance with one embodiment of the present inventions;

FIG. 5 is a perspective view of a robotic catheter assembly used in themedical robotic system of FIG. 4;

FIG. 6 is a perspective view of the catheter assembly used in therobotic catheter assembly of FIG. 5;

FIG. 7 is a plan view of one catheter having a single region ofarticulation with four pullwires for use in the catheter assembly ofFIG. 6;

FIGS. 7A-7C are cross-sectional views of the catheter of FIG. 7,respectively taken along the lines 7A-7A, 7B-7B, and 7C-7C;

FIG. 8 is a perspective view of an adapter used to transition pullwiresfrom one circumferential orientation to another circumferentialorientation in the catheter of FIG. 7;

FIG. 9 is another perspective view of the adapter of FIG. 8;

FIG. 10 is a diagram showing the neutral axis of the bend in a distalarticulating section of the catheter of FIG. 7;

FIG. 11 is a cross-sectional view of the proximal shaft of the catheterof claim 7, particularly showing the location of a neural bending axisrelative to the pullwires;

FIG. 12 is a cross-sectional view of the proximal shaft of a prior artcatheter of claim 7, particularly showing the location of a neuralbending axis relative to the pullwires;

FIG. 13 is a plan view of one catheter having a single region ofarticulation with three pullwires for use in the catheter assembly ofFIG. 6;

FIGS. 13A-13C are cross-sectional views of the catheter of FIG. 13,respectively taken along the lines 13A-13A, 13B-13B, and 13C-13C;

FIG. 14 is a perspective view of an adapter used to transition pullwiresfrom one circumferential orientation to another circumferentialorientation in the catheter of FIG. 13;

FIG. 15 is a top view of the adapter of FIG. 14;

FIG. 16 is another perspective view of the adapter of FIG. 14;

FIG. 17 is a plan view of a rapid exchange catheter having a singleregion of articulation with four pullwires for use in the catheterassembly of FIG. 18;

FIGS. 17A-17C are cross-sectional views of the catheter of FIG. 17,respectively taken along the lines 17A-17A, 17B-17B, and 17C-17C;

FIG. 18 is a side view of a rapid exchange catheter assembly that canalternatively be used in the robotic catheter assembly of FIG. 5;

FIG. 19 is a plan view of one catheter having two regions ofarticulation with four pullwires for use in the catheter assembly ofFIG. 6;

FIGS. 19A-19C are cross-sectional views of the catheter of FIG. 19,respectively taken along the lines 19A-19A, 19B-19B, and 19C-19C;

FIGS. 20 and 21 are plan views showing one method of accessing the leftcoronary artery of an anatomy using the catheter of FIG. 19;

FIG. 20A is a cross-sectional view of the distal articulating region ofthe catheter shown in FIG. 20, respectively taken along the line20A-20A;

FIG. 21A is a cross-sectional view of the proximal articulating regionof the catheter shown in FIG. 21, respectively taken along the line21A-21A;

FIGS. 22 and 23 are plan views showing one method of accessing the rightcoronary artery of an anatomy using the catheter of FIG. 19;

FIG. 22A is a cross-sectional view of the distal articulating region ofthe catheter shown in FIG. 20, respectively taken along the line22A-22A;

FIG. 23A is a cross-sectional view of the proximal articulating regionof the catheter shown in FIG. 23, respectively taken along the line23A-23A;

FIGS. 24A-24C are plan views showing methods of accessing the leftcoronary arteries of different anatomies using the catheter of FIG. 19;

FIG. 25 is a plan view of another catheter having two regions ofarticulation with four pullwires for use in the catheter assembly ofFIG. 6;

FIGS. 25A-25D are cross-sectional views of the catheter of FIG. 25,respectively taken along the lines 25A-25A, 25B-25B, 25C-25C, and25D-25D;

FIG. 26 is a plan view of a multi-bend segment of the catheter of FIG.25, particularly showing a distal articulation angle and a proximalarticulation angle;

FIG. 27 is a plan view showing a method of accessing a renal arteryusing the catheter of FIG. 25;

FIG. 28 is a control diagram illustrating a multi-bend algorithm thatcontrol the distal articulating section and proximal articulatingsection of the catheter of FIG. 25;

FIG. 29 is a diagram illustrating the moment applied to the transitionsection of the catheter of FIG. 25 caused by the pullwires extendingthrough the transition section;

FIGS. 30A and 30B are plan views showing one method of accessing theright coronary artery of an anatomy using the catheter of FIG. 25;

FIGS. 31A-31I are plan views illustrating one method of directlyanchoring a pullwire to the braid of a steerable catheter;

FIG. 32 is a plan view illustrating one embodiment of a braiding machinethat can be used to braid a catheter for use in the catheter assembly ofFIG. 6;

FIGS. 33A and 33B are front views of interchangeable nose cones that canbe used in the braiding machine of FIG. 32;

FIG. 34 is a plan view illustrating another embodiment of a braidingmachine that can be used to braid a catheter for use in the catheterassembly of FIG. 6;

FIG. 35 is a front view of a nose cone that can be used in the braidingmachine of FIG. 34;

FIG. 36 is a perspective view of an iris assembly that can be used inthe nose cone of FIG. 35;

FIG. 37 is a side view of the iris assembly of FIG. 36;

FIG. 38 is an axial view of the iris assembly of FIG. 36, particularlyshowing the iris assembly in a first position that groups three wiremandrels circumferentially adjacent each other;

FIG. 39 is an axial view of the iris assembly of FIG. 36, particularlyshowing the iris assembly in a second position that spaces three wiremandrels equidistant from each other;

FIG. 40 is an axial view of a first iris plate for use in the irisassembly of FIG. 36;

FIG. 41 is an axial view of a second iris plate for use in the irisassembly of FIG. 36; and

FIG. 42 is an axial view of a third iris plate for use in the irisassembly of FIG. 36.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring to FIG. 4, one embodiment of a robotic catheter system 10constructed in accordance with the present invention will now bedescribed. The system 10 generally comprises an operating table 12having a movable support-arm assembly 14, an operator control station 16located remotely from the operating table 12, and a robotic catheterassembly 18 mounted to the support-arm assembly 14 above the operatingtable 12. Exemplary robotic catheter systems that may be modified forconstructing and using embodiments of the present invention aredisclosed in detail in the following U.S. patent applications, which areall expressly incorporated herein by reference in their entirety: U.S.patent application Ser. No. 11/678,001, filed Feb. 22, 2007; U.S. patentapplication Ser. No. 11/073,363, filed Mar. 4, 2005; U.S. patentapplication Ser. No. 11/179,007, filed Jul. 6, 2005; U.S. patentapplication Ser. No. 11/418,398, filed May 3, 2006; U.S. patentapplication Ser. No. 11/481,433, filed Jul. 3, 2006; U.S. patentapplication Ser. No. 11/637,951, filed Dec. 11, 2006; U.S. patentapplication Ser. No. 11/640,099, filed Dec. 14, 2006; U.S. PatentApplication Ser. No. 60/833,624, filed Jul. 26, 2006; and U.S. PatentApplication Ser. No. 60/835,592, filed Aug. 3, 2006.

The control station 16 comprises a master input device 20 that isoperatively connected to the robotic catheter assembly 18. A physicianor other user 22 may interact with the master input device 20 to operatethe robotic catheter assembly 18 in a master-slave arrangement. Themaster input device 20 is connected to the robotic catheter assembly 18via a cable 24 or the like, thereby providing one or more communicationlinks capable of transferring signals between the control station 16 andthe robotic catheter assembly 18. Alternatively, the master input device20 may be located in a geographically remote location and communicationis accomplished, at least in part, over a wide area network such as theInternet. The master input device 20 may also be connected to therobotic catheter assembly 18 via a local area network or even wirelessnetwork that is not located at a geographically remote location.

The control station 16 also comprises one or more monitors 26 used todisplay various aspects of the robotic instrument system 10. Forexample, an image of the sheath and leader catheter (described infurther detail below) may be displayed in real time on the monitors 26to provide the physician 22 with the current orientation of the variousdevices as they are positioned, for example, within a body lumen orregion of interest. The control station 16 further comprises a processorin the form of a computer 28, which may comprise a personal computer orother type of computer work station for accurately coordinating andcontrolling actuations of various motors within robotic catheterassembly 18.

The support-arm assembly 14 is configured for movably supporting therobotic catheter assembly 18 above the operating table 12 to provideconvenient access to the desired portions of the patient (not shown) andprovide a means to lock the catheter assembly 18 into positionsubsequent to the preferred placement. In this embodiment, thesupport-arm assembly 14 comprises a series of rigid links 30 coupled byelectronically braked joints 32, which prevent joint motion whenunpowered, and allow joint motion when energized by the control station16. In an alternative embodiment, the rigid links 30 may be coupled bymore conventional mechanically lockable joints, which may be locked andunlocked manually using, for example, locking pins, screws, or clamps.The rigid links 30 preferably comprise a light but strong material, suchas high-gage aluminum, shaped to withstand the stresses and strainsassociated with precisely maintaining three-dimensional position of theweight of the catheter assembly 18.

Referring further to FIGS. 5 and 6, the robotic catheter assembly 18will now be described in detail. The robotic catheter assembly 18comprises a robotic instrument driver 34, a robotic guide sheath 36, arobotic leader catheter 38, and a guide wire 40 mounted to theinstrument driver 34 in a coaxial relationship. The robotic catheterassembly 18 may also include a drape (not shown) that covers theinstrument driver 34. As will be described in further detail below, theinstrument driver 34 provides robotic steering actuation, as well asrobotic insertion and retraction actuation, to the guide sheath 36,working catheter 38, and guide wire 40 in accordance with controlsignals transmitted from the control station 16 (shown in FIG. 4). Theguide sheath 36 generally includes a sheath body 42 having a proximalend 44 and a distal end 46, as well as a proximal interface in the formof a guide sheath steering adapter 48 (“splayer”) operably coupled tothe proximal end 44 of the sheath body 42. The leader catheter 38generally includes a catheter body 50 having a proximal end 52 and adistal end 54, as well as a proximal interface in the form of a leadercatheter steering adapter 56 operably mounted to the proximal end 52 ofthe catheter body 50. The guide wire 40 generally includes a guide wirebody 58 having a proximal end 60 and a distal end 62.

The instrument driver 34 comprises a housing 64 that contains motors(not shown). The respective adapters 48, 56 and the proximal end 60 ofthe guide wire body 58 are mechanically interfaced to the housing 64 insuch a manner that they may be axially displaced relative to each othervia operation of the motors, thereby effecting insertion or retractionmovements of the respective guide sheath 36, leader catheter 38, andguide wire 40 relative to each other, and thus, relative to theoperating table 12 (shown in FIG. 4).

To this end, the guide sheath 36 comprises a working lumen (not shown inFIGS. 5 and 6) that extends all the way through the sheath body 42. Thegeometry and size of the working lumen will be selected in accordancewith the cross-sectional geometry and size of the lead catheter 38. Thesheath body 42 may be composed of a low-friction inner layer (e.g., acoating of silicone or polytetrafluoroethylene) to provide alow-friction surface to accommodate movement of the leader catheter 38within the working lumen. The lead catheter 38 passes through the lumenof the guide sheath 36, and is thus, moveable relative thereto. As shownin FIGS. 5 and 6, the leader catheter 38 projects distally with respectto the distal end 46 of the sheath body 42. Of course, the leadercatheter 38 may be withdrawn proximally such that its distal end 54 issubstantially flush with the distal end 46 of the sheath body 42, orwithdrawn proximally even further such that its distal end 54 isdisposed within the distal end 46 of the sheath body 42. The leadercatheter 38 may be movably positioned within the working lumen of theguide sheath 36 to enable relative insertion of the two devices,relative rotation, or “roll” of the two devices, and relative steeringor bending of the two devices relative to each other, particularly whenthe distal end 54 of the leader catheter 38 is inserted beyond thedistal tip of the guide sheath 36.

Similarly, the leader catheter 38 comprises a working lumen (not shownin FIGS. 5 and 6) that extends at least partially through the catheterbody 50. The geometry and size of the working lumen will be selected inaccordance with the cross-sectional geometry and size of the guide wire40. The catheter body 50 may be composed of a low-friction inner layer(e.g., a coating of silicone or polytetrafluoroethylene) to provide alow-friction surface to accommodate movement of the guide wire 40 withinthe working lumen. The guide wire 40 passes through the lumen of theleader catheter 38, and is thus, moveable relative thereto. As shown inFIGS. 5 and 6, the guide wire 40 projects distally with respect to thedistal end 54 of the catheter body 50. Of course, the guide wire 40 maybe withdrawn proximally such that its distal end 62 is substantiallyflush with the distal end 54 of the catheter body 50, or withdrawnproximally even further such that its distal end 62 is disposed withinthe distal end 62 of the catheter body 50. The guide wire 40 may bemovably positioned within the working lumen of the leader catheter 38 toenable relative insertion of the two devices, relative rotation, or“roll” of the two devices, and relative steering or bending of the twodevices relative to each other, particularly when the distal end 62 ofthe guide wire 40 is inserted beyond the distal tip of the leadercatheter 38. Notably, by movably positioning the guide wire 40 relativeto the leader catheter 38, and movably positioning the leader catheter38 relative to the guide sheath 36, the bending stiffness of theassembly may be varied as needed to optimize the tracking ability of theleader catheter 38.

Each of the adapters 48, 56 also comprises one or more rotating spoolsor drums 66 that can selectively tension or release pullwires (not shownin FIG. 6) disposed within the respective sheath body 42 and catheterbody 50, thereby effecting a single articulation (and optionally,multiple articulations) of the distal ends 46, 54 of the sheath andcatheter bodies 42, 50. In the illustrated embodiment, each of theadapters 48, 56 comprises four rotating spools or drums 66 (only oneshown for the proximal adapter 48, and only three shown for the proximaladapter 56) for four corresponding pullwires. The instrument driver 34further comprises a guide wire driver 68 to which the proximal end ofthe guide wire body 58 is affixed. The distal end 62 of the guide wirebody 58 may have a J-shape as is conventional for guide wires. Each ofthe adapters 48, 56 and guide wire driver 68 may optionally be capableof rotating or rolling the sheath body 42, catheter body 50, and guidewire body 58 relative to each other.

With reference now to FIG. 7, an embodiment of a flexible and steerableelongate catheter 100 will be described. The catheter 100 can be used aseither of the guide sheath 36 or leader catheter 38 illustrated in FIGS.5 and 6, and can be operably coupled to the instrument driver 34 via aproximal adapter 101 (e.g., either of proximal adapters 48, 56). Thecatheter 100 is substantially pliable or flexible, such that when it isadvanced into a patient, an operator or surgeon may easily manipulatethe catheter 100 to conform, adopt, or match the shape or curvatures ofthe internal pathways (e.g., gastrointestinal tract, blood vessels,etc.) of the patient.

The catheter 100 generally includes an elongate catheter body 102, whichin the illustrated embodiments, has a circular cross-section, althoughother cross-sectional geometries, such as rectangular, can be used. Aswill be described in further detail below, the catheter body 102 may becomprised of multiple layers of materials and/or multiple tubestructures that exhibit a low bending stiffness, while providing a highaxial stiffness along the neutral axis. Typical designs include anitinol spine encapsulated in braid and any flexible, pliable, orsuitable polymer material or bio-compatible polymer material or abraided plastic composite structure composed of low durometer plastics(e.g., nylon-12, Pebax®, polyurethanes, polyethylenes, etc.).

The catheter 100 further includes a working lumen 104 disposed throughthe entire length of the catheter body 102 for delivering one or moreinstruments or tools from the proximal end of the catheter body 102 tothe distal end of the catheter body 102. The nature of the working lumen104 will depend on the intended use of the catheter 100. For example, ifthe catheter 100 is to be used as the guide sheath 36 (shown in FIG. 6),the working lumen 104 will serve to accommodate the leader catheter orworking catheter 38 (shown in FIG. 6). If the catheter 100 is to be usedas a leader catheter or working catheter, the working lumen 104 willserve to accommodate a guide wire 40 (shown in FIG. 6).

To enable steering, the catheter 100 further includes a control ring 106(shown in phantom) secured around the working lumen 104 at any location,section, portion, or region along the length of the catheter body 102, aplurality of pullwires 108 housed within one or more lumens 110extending through the catheter body 102, and a proximal adapter (notshown). Each of pullwires 108 may be a metallic wire, cable or filament,or it may be a polymeric wire, cable or filament. The pullwire 108 mayalso be made of natural or organic materials or fibers. The pullwire 108may be any type of suitable wire, cable or filament capable ofsupporting various kinds of loads without deformation, significantdeformation, or breakage.

The distal ends of the pullwires 108 are anchored or mounted to thecontrol ring 106, such that operation of the pullwires 108 may applyforce or tension to the control ring 106, which may steer or articulate(e.g., up, down, pitch, yaw, or any direction in-between) the pertinentlocation, section, portion, or region of the catheter 100, which may ineffect provide or define various bend radii for the articulated portionof the catheter 100. In the illustrated embodiment, the control ring 106is secured to the distal end of the catheter 100, and therefore, thedistal end of the catheter 100 will articulate when any of the pullwires108 are tensioned. The proximal ends of the pullwires 108 terminate inthe proximal adapter 101, and in particular, spools or drums 103 locatedwithin the proximal adapter 101. Thus, robotic or manual actuation ofthe proximal interface will cause the pertinent location, section,portion, or region of the catheter 100 to articulate in the direction ofthe pullwire or pullwires 108 that are tensioned. The catheter 100 mayalternatively be manually controlled, in which case, it may include aconventional manually controlled steerable interface (not shown).

In other embodiments, no control ring may be used. Instead, the distalends of the pullwires 108 may be attached directly to a section orportion of the catheter body 102 where it may be steered, articulated,or bent, as described in an alternative embodiment below. The wires maybe crimped, soldered, welded or interlocked in any suitable manner to aspecific location on a bending section or portion of the catheter body102. In some embodiments there may be more than one control ring 106secured to the catheter body 102 or more than one control wireattachment control locations, sections, or portions for controlling,steering, or articulating more than one section or portion of thecatheter body 102, e.g., into various complex shapes or curvatures(e.g., “S” curved shapes or “J” curved shapes, etc.). For example, thecatheter 100 may be steered, articulated, or deflected into variouscomplex shapes or curvatures that may conform to various complex shapesor curvatures of internal pathways of a patient to reach a target tissuestructure of an organ inside the patient.

In this embodiment, the catheter 100 is functionally divided into foursections: a distal tip 112, a distal articulating section 114, atransition section 116, and a proximal shaft section 120.

The distal tip 112 includes an atraumatic rounded tip portion 122 and acontrol portion 124 in which the control ring 106 is mounted. The distaltip 112 also includes an exit port (not shown) in communication with theworking lumen 104 and from which a working catheter or guidewire mayextend distally therefrom. In one embodiment, the atraumatic rounded tipportion 122 is 2 mm in length and is composed of a suitable polymermaterial (e.g., Pebax® 55D/35D); and the control portion 124 is 1 mm inlength and is composed of a suitable polymer material (e.g., Pebax®35D).

In the distal articulating section 114, there are four pullwire lumens110 that are equally spaced in an arcuate manner (i.e., ninety degreesapart), and thus, the four corresponding pullwires 108 are equallyspaced as well. In an alternative embodiment, a different number ofpullwires lumens 110, and thus, pullwires 108, can be used. For example,three pullwire lumens 110, and thus three pullwires 108, can be equallyspaced in an arcuate manner (i.e., one hundred twenty degrees apart) inthe distal articulating section 114. Thus, the pullwires 108 are mountedto the control ring 106 in orthogonal positions (i.e., ninety degreesapart), such that tensioning one of the pullwires 108 will selectivelyarticulate the distal articulating section 114 in one of four orthogonaldirections. Tensioning two of the pullwires 108 will allow the pertinentsection to be articulated in an infinite number of directions(effectively, providing two degrees of freedom: pitch and roll).

The distal articulating section 114 preferably allows for a moderatedegree of axial compression and optimal lateral flexibility. In oneembodiment, the distal articulating section 114 is 30 mm in length. Thepullwire lumens 110 extend through the distal articulating section 114and may be constructed of a low friction material or may simply beunsupported tubular cavities in which the pullwires 108 respectivelyfloat. The entire working lumen 104 within the distal articulatingsection 114 is formed by an inner polymer tube (e.g., 0.001″ thickPTFE). The distal articulating section 114 has a several portions ofdiffering rigidities formed by having different polymer outer tubes. Forexample, the distal articulating section 114 may include a 5 mm rigidportion 126 having a moderately rigid outer polymer tube (e.g., Pebax®55D) and a 25 mm articulatable portion 128 having an outer tube composedof a relatively flexible outer polymer tube (e.g., Pebax® 35D). Thelength of the articulatable portion 128 can vary depending on theperformance requirements for the catheter 100. A longer articulatableportion 128 may be beneficial to increase the area of reach, while ashorter articulatable portion 128 may be beneficial for cannulatingtight side branches in the anatomical vasculature. To increase its axialrigidity and elastic properties, the articulatable portion 128 comprisesa double braided layer (e.g., sixteen 0.0005″×0.003″ spring temper 304Vstainless steel wires braided at 68 picks per inch (ppi) in a 2 over 2pattern) embedded within the outer polymer tube. As will be described infurther detail below, the distal ends of the pullwires 108 may bedirectly anchored between the two layers of the braid.

The transition section 116 resists axial compression to clearly definethe proximal end of the distal articulating section 114 and transfer themotion of the pullwires 110 to the distal articulating section 114,while maintaining lateral flexibility to allow the catheter 100 to trackover tortuous anatomies. The transition section 136 may be 28 mm inlength and be composed of an outer polymer tube (e.g., Pebax® 55D).Significantly, the transition section 116 transitions the four lumens110 in the distal articulating section 114 to a single hollow stiffeningtube 130 in the proximal shaft section 120. With further reference toFIGS. 8 and 9, the illustrated embodiment accomplishes this by using amolded adapter 138, which may be mounted within the outer polymer tubeof the transition body section 120.

The adapter 138 includes an adapter body 140 having a proximal end 142that interfaces with stiffening tube 130 in the proximal shaft section120, and a distal end 144 that interfaces with the four pullwire lumens110 in the distal articulating section 114. The adapter body 140 may becomposed of a suitable rigid material, such as stainless steel or aglass-filled or high durometer plastic. The adapter 138 further includesa plurality of channels 146 formed in the external surface of theadapter body 140, a square-shaped boss 148 formed at the distal end 144of the adapter body 140, a plurality of lumens 150 extending throughboss 148, and a single port 152 formed in the proximal end 142 of theadapter body 140. The lumens 150 within the boss 148 are equally spacedfrom each other in coincidence with the equally spaced lumens 110 in thedistal articulating section 114 of the catheter 100. In particular, thefour lumens 150 are respectively disposed through the four corners ofthe boss 148. The lumens 150 within the boss 148 are also respectivelycoincident with the distal ends of the channels 146, and the single port152 is coincident with the proximal ends of the channels 146. One of thechannels 146 linearly extends along the length of the adapter body 140,while the remaining three channels 146 spiral around the length of theadapter body 140, so that the proximal ends of all four channels 146converge into the single port 152. Thus, the four pullwires 108 extendproximally from the distal articulating section 114, into the lumens 150formed in the boss 148 of the adapter body 140, along the channels 146,into the single port 152, and then into the stiffening tube 130.

The adapter 138 further includes a working lumen 154 extending throughthe boss 148 and a distal portion of the adapter body 140. The distalend of the working lumen 154 is in coincidence with the portion of theworking lumen 104 extending through the distal articulating section 114.The proximal end of the working lumen 130 exits the adapter body 140just proximal to the single port 152, such that it is in coincidencewith the lumen of the transition section 136, which, in turn, is incoincidence with the working lumen 104 extending through the proximalshaft section 120. In the same manner that the working lumen 104 andstiffening tube 130 are offset from the axis of the proximal shaftsection 120 (as described below), the working lumen 154 and single port152 are offset from the axis of the adapter body 140. It should beappreciated that the use of the adapter 138 allows the four pullwires108 to be transitioned from the respective lumens 110 of the distalarticulating section 114 into the single stiffening tube 130 withouthaving to spiral the pullwires 108 and corresponding lumens through thewall of the catheter tube 102, thereby allowing the thickness of thewall to be uniform and minimizing the possibility of weakened regions inthe catheter tube 102 and possible inadvertent kinking. Therefore, it isparticularly suitable for thin walled catheters.

As will be described below in further embodiments, where wallthicknesses are not as thin, instead of using the adapter 140, theequally spaced pullwire lumens 110 from the distal articulating section114 may be gradually converged via the transition section 116 onto oneside of the proximal shaft section 120 and into the stiffening tube 130.

Referring back to FIG. 7, the proximal shaft section 120 combineslateral flexibility (which is needed for optimal tracking) with axialstiffness (which is needed for optical articulation performance). Theproximal shaft section 120 represents the majority of the length of thecatheter 100. The entire working lumen 104 within the proximal shaftsection 120 is formed by an inner polymer tube (e.g., 0.001″ thickPTFE).

The proximal shaft section 120 gradually transitions the catheter 100from the transition section 116 to the more rigid remaining portion ofthe catheter 100 by having several portions of differing rigiditiesformed by having different polymer outer tubes. For example, theproximal shaft section 120 may include a first 6 mm proximal portion 132including outer polymer tube (e.g., Pebax® 55D); a second 7.5 mmproximal portion 134 including an outer polymer tube (e.g., Pebax® 72D)that is more laterally rigid than the outer polymer tube in the firstproximal portion 128; and a third lengthy (e.g., 1 meter long) proximalshaft section 136 including an outer polymer tube (e.g., Nylon-12) thatis resistant to rotational forces to reduce the effect of curvealignment when the catheter 100 is contorted to the tortuous anatomy. Toincrease its axial rigidity, the proximal shaft section 120 comprises adouble braided layer (e.g., sixteen 0.0005″×0.003″ spring temper 304Vstainless steel wires braided at 68 picks per inch (ppi) in a 2 over 2pattern) embedded within the outer polymer tube.

Significantly, unlike with the distal articulating section 114 in whichthe pullwires 108 are disposed in equally spaced apart lumens, thepullwires 108 in the proximal shaft section 120 are disposed in one ormore lumens on one arcuate side of the proximal shaft section 120. Inthe illustrated embodiment, the one or more lumens takes the form of thepreviously mentioned stiffening tube 130 disposed along the catheterbody 102 along the proximal shaft section 120, and through which thepullwires 108 are housed and passed back to the proximal adapter 101. Aswill be described in further embodiments below, the one or more lumensmay take the form of a plurality of tubes that respectively house thepullwires 108.

The inner diameter of the stiffening tube 130 is preferably large enoughto allow the pullwires 108 to slide freely without pinching each other.The stiffening tube 130 is composed of a material that is more axiallyrigid than the surrounding material in which the catheter body 102 iscomposed. For example, the stiffening tube 130 may take the form of astainless steel hypotube or coil pipe, while the catheter body 102 alongthe proximal shaft section 120 may be composed of a more flexiblepolymer or polymer composite, as will be described in further detailbelow. The stiffening tube 130 must be laminated into the catheter body102, thereby allowing the stiffening tube 130 to support the axial loadson the catheter 100 from the tensioning of the pullwires 108. Due to thenon uniform stiffness in the catheter cross section, the neutral axiswill no longer be in the geometric center of the catheter body 102 alongthe proximal shaft section 120, but rather be shifted closer to the axisof the stiffening tube 130, thereby minimizing the impact on bendingstiffness. Thus, by locating the pullwires 108 in one lumen (i.e., thestiffening tube 130) in the catheter body 102, and designing thecatheter body 102 to be relatively flexible, thereby controlling thelocation of the neutral axis, an axially stiff, but laterally flexible,proximal shaft section 120 can be achieved.

The effects of bending stiffness relative to the neutral axis will nowbe described. The neutral axis can be considered the axis in thecross-section of a beam or shaft along which there are no longitudinalstresses or strains when the beam or shaft is bent. If the cross-sectionof the beam or shaft is symmetrical, isotropic, and is not curved beforea bend occurs, then the neutral axis is at the geometric centroid of thecross-section. When the bend occurs, all fibers on one side of theneutral axis are in a state of tension, while all fibers on the otherside of the neutral axis are in a state of compression. As shown in FIG.10, the axial strain ε is given by the ratio y/R, where y is thedistance from the neutral axis, and R is the radius of curvature of theneutral axis. It follows that the axial stress σ at any point is givenby EKy, where E is the modulus of elasticity and κ is the curvature ofthe beam or shaft. Thus, the axial stress σ is also proportional to thedistance from the neutral axis y. Therefore, when high stiffness membersare further from the neutral axis, the bending stress and hence bendingstiffness is higher.

It follows that when the pullwires 108 (and any axially stiffcompressive members that provide the reaction force) are located closerto the neutral axis, the bending stiffness of the proximal shaft section120 is decreased. That is, as shown in FIG. 11, there is only one stiffmember (i.e., the stiffening tube 130) that supports the axial load ofthe pullwires 108, and therefore, the neutral axis (represented by theasterisk) of the proximal shaft section 120 will be close to thelocation of the stiffening tube 130. Ultimately, the exact location ofthe neutral axis will depend on the relative stiffness of the stiffeningtube 130 relative to the remainder of the material in the proximal shaftsection 120. Therefore, each of the pullwires 108 will be relativelyclose to the neutral axis. Notably, the working lumen 104 is offset fromthe geometric center of the proximal shaft section 120 in order toaccommodate the stiffening tube 130. In contrast, as shown in FIG. 12, aconventional symmetrical arrangement may distribute four stiffeningmembers 130 a about the geometric center of the proximal shaft section130 a, and therefore, the neutral axis of the proximal shaft section 130a will essentially be at its geometric center. As a result, thepullwires 108 a will be relatively far from this neutral axis. Thus, itcan be appreciated from a comparison between FIGS. 11 and 12 that themaximum distance from any of the pullwires 108 to the neutral axis inthe preferred embodiment is far shorter than the pullwires 108 a to theneutral axis in the conventional design.

Therefore, by having the pullwires 108 close to or on the neutral axis,the pullwires 108 will have a minimum change in length during anexternally applied shaft curvature. This achieves consistentarticulation of the distal articulating section 114 independent of thecurvature of the proximal shaft section 120. In other words, theproximal shaft section 120 does not need to be maintained substantiallystraight in contrast to the conventional pullwire arrangement, whichrequires the operator to maintain the proximal shaft section relativelystraight. Thus, locating the pullwires 108 close to the neutral axis ofthe proximal shaft section 120 allows the operator to traverseanatomical features, such as the iliac bifurcation or the aorticarch—not just with the flexible distal articulating section 108, butwith the entire catheter 100 as required, while at the same time havingfull control of the distal tip of the catheter 100.

Furthermore, because the proximal shaft section 120 is relativelyaxially stiff, articulation of the distal articulating section 114 bytensioning one or more of the pullwires 108 will not cause significantlateral deflection of the proximal shaft section 120, thereby improvinginstrument stability. Furthermore, because the pullwires 108 are closeto the neutral axis in the proximal shaft section 120, there is only asmall radial distance between the pullwires 108 and the neutral axis.This radial distance is what causes the bending moment that leads toarticulation of the distal articulating section 114 (or any otherarticulating section). With small bending moments generated bytensioning the pullwires 108, there will be minimal articulation of theproximal shaft section 120. Therefore, varying the position of theneutral axis with respect to the position of the pullwires 108 in anysection of the catheter 100 can influence how much the distalarticulating section 114 will bend when a given load is applied to apullwire 108. For example, the distal articulation section 114 has theneutral axis in the geometric center and when any tension is applied toone or more pullwires 108, a moment will be generated and the distal tip112 will articulate. On the other hand, the proximal shaft section 120will not tend to bend and hence twist during tensioning of those samepullwires 108 of the distal articulating section 114 because of thesmaller moment arm, thereby minimizing the tendency for the catheter 100to curve align. Notably, even if a tensioned pullwire 108 initiallycauses curve alignment by moving to the inside of the curved proximalshaft section 120, the catheter 100 will be stable thereafter, since allthe pullwires 108 are located on one arcuate side of the catheter body102. That is, once the stiffening tube 130, and thus the pullwires 108,move to the inside of the curved proximal shaft section 120, any of thepullwires 108 can be tensioned without causing further rotation of thecurved proximal shaft section 120, thereby allowing the distalarticulating section 114 to be articulated in the desired direction.Furthermore, because only one stiffening tube 130 is utilized, asopposed to four separate stiffening tubes or coil pipes, for therespective four pullwires 108, there is a significant reduction in costand a consistent low bending stiffness irrespective of the articulationloads applied to the pullwires 108.

Having described the construction of the catheter 100, one method ofmanufacturing the catheter 100 will now be described. In this method,the distal articulating section 114 and proximal shaft section 120 arefabricated separately, and then mounted to each other when thetransition section 136 is fabricated. The distal tip 112 can then beformed onto the assembly to complete the catheter 300.

The distal articulating section 114 can be fabricated by first insertinga copper wire process mandrel through a lumen of an inner polymer tube(e.g., a PTFE extrusion) having the intended length of the distalarticulating section 114. Then, using a braiding machine (embodiments ofwhich will be described in further detail below), a first layer ofbraiding is laid down over the length of the inner polymer tube. Next,four PTFE-coated stainless steel wire process mandrels are respectivelydisposed over the length of the braided inner polymer tube in fourequally spaced circumferential positions (i.e., clocked ninety degreesfrom each other), and a second layer of braiding is laid down over thefour wire process mandrels. Next, outer polymer tubes having differentdurometers and lengths corresponding to the lengths of the differentportions of the distal articulating section 114 (e.g., a Pebax® 55Dextrusion for the rigid section 120 and a Pebax® 35D extrusion for thearticulatable section 122) are slid over the fully braided inner polymertube, and then heat shrink tubing is slid over the outer polymer tubes.The assembly is then heated to a temperature above the meltingtemperature of the outer polymer tubes, but below the meltingtemperature of the heat shrink tubing. As a result, the outer polymertubes are laminated to the assembly. In particular, the outer polymertubes melt and flow, while the heat shrink tubing shrinks and compressesthe melted polymer tubes into the braid and around the four stainlesssteel process mandrels. The assembly then cools and solidifies tointegrate the inner polymer tube, braid, and outer polymer tubestogether. Then, the center copper wire can be pulled from the assemblyto create the working lumen 104, and the four stainless steel wires canbe pulled from the assembly to respectively create the four pullwirelumens 110.

In a similar manner, the proximal shaft section 120 can be fabricated byfirst inserting a copper wire process mandrel and the stiffening tube130 through respective offset lumens of an inner polymer tube (e.g., aPTFE extrusion) having the intended length of the proximal shaft section120. Then, using a conventional braiding machine, two layers of braidingare laid down over the length of the inner polymer tube. Next, outerpolymer tubes having different durometers and lengths corresponding tothe lengths of the different portions of the first proximal shaftsection 120 (e.g., a Pebax® 55D extrusion for the proximal portion 130,a Pebax® 72D extrusion for the second proximal portion 132, and aNylon-12 extrusion for the third proximal portion 134) are slid over thefully braided inner polymer tube, and then heat shrink tubing is slidover the outer polymer tubes. The assembly is then heated to atemperature above the melting temperature of the outer polymer tubes,but below the melting temperature of the heat shrink tubing. As aresult, the outer polymer tubes are laminated to the assembly. Inparticular, the outer polymer tubes melt and flow, while the heat shrinktubing shrinks and compresses the melted polymer tubes into the braidand around the four stainless steel process mandrels. The assembly thencools and solidifies to integrate the inner polymer tube, braid,stiffening tube 130, and outer polymer tubes together. Then, the centercopper wire can be pulled from the assembly to create the working lumen104.

Next, the distal articulating section 114 and proximal shaft section 120are coupled to each other by fabricating the transition section 136between the distal articulating section 114 and proximal shaft section120. In particular, a center wire process mandrel is inserted throughthe working lumen 154 of the adapter 138 and four wire process mandrelsare inserted through the single port 152, four channels 146, and fourlumens 150 of the adapter 138. The proximal end of the center wireprocess mandrel is then inserted through the working lumen 104 in theproximal shaft section 120, and the distal end of the center wireprocess mandrel is then inserted through the working lumen 104 in thedistal articulating section 114. The proximal ends of the four wireprocess mandrels are inserted through the stiffening tube 130 in theproximal shaft section 120, and the distal ends of the four wire processmandrels are inserted through the pullwire lumens 110 in the distalarticulating section 114. The proximal shaft section 120 and distalsection 116 are then moved towards each other until they abut theopposite ends of the adapter 138.

Next, an outer polymer tube having a durometer and length correspondingto the length of the transition catheter 136 (e.g., Pebax® 55D) is slidover the adapter 138, and then heat shrink tubing is slid over the outerpolymer tube. The assembly is then heated to a temperature above themelting temperature of the outer polymer tube, but below the meltingtemperature of the heat shrink tubing. As a result, the outer polymertube is laminated to the assembly. In particular, the outer polymer tubemelts and flows, while the heat shrink tubing shrinks and compresses themelted polymer tube into the desired cylindrical shape. The assemblythen cools and solidifies to integrate the inner polymer tube, adapter138, and outer polymer tube together. Then, the center copper wire canbe pulled from the assembly to create the working lumen 104.

Then, the proximal ends of the pullwires 108, which may be pre-fastened(e.g., soldered, welded, brazed, or glued) to the control ring 106, areinserted into the pullwire lumens 110 at the distal end of the catheterbody 102, and advanced through the lumens 110 until they exit theproximal end of the catheter body 102. The control ring 106 is then slidover the distal end of the central wire process mandrel extending fromthe distal articulating section 114 until it abuts the rigid portion 120of the distal articulating section 114. Then, outer polymer tubes havingdifferent durometers and lengths corresponding to the lengths of thedifferent portions at the distal tip 112 (e.g., a Pebax® 55D/35Dextrusion for the tip portion 122, and a Pebax® 35D extrusion for thecontrol portion 124) are slid over the center wire process mandrel andcontrol ring 106, and then heat shrink tubing is slid over the outerpolymer tubes. The assembly is then heated to a temperature above themelting temperature of the outer polymer tube, but below the meltingtemperature of the heat shrink tubing. As a result, the outer polymertube melts and flows, while the heat shrink tubing shrinks andcompresses the melted polymer tube into the desired cylindrical shape.The assembly then cools and solidifies to integrate the inner polymertube, adapter 138, and outer polymer tube together. Then, the distal tip122 can be cut to a rounded shape, and the center wire process mandrelcan be pulled from the catheter 100. The proximal end of the cathetertube 102 can then be mounted to the proximal adapter 100, and theproximal ends of the pullwires 108 can be installed on the spools ordrums 103 of the proximal adapter 101.

As briefly discussed above, instead of utilizing a control ring 106, thedistal ends of the pullwires 108 may be attached directly to a sectionor portion of the catheter body 102 where it may be steered,articulated, or bent. In particular, the working lumen 104 and pullwirelumens 110 are formed and the braid and outer polymer tubes are appliedto the inner polymer tube in the same manner described above, with theexception that the distal ends of the pullwires 108 are anchored betweenthe braid layers (or alternatively, layers of a different type of wiresupport structures, such as a coil or mesh), as illustrated in FIGS.31A-31I. The wire support structure may be made of metal, plastic,fabric, thread, or any other suitable material.

The distal articulating section 114 is fabricated by disposing a firstlayer of braiding over the length of the inner polymer tube (FIG. 31A),four PTFE-coated stainless steel wire process mandrels (only one shownfor purposes of clarity) are respectively disposed over the length ofthe braided inner polymer tube in four equally spaced circumferentialpositions (i.e., clocked ninety degrees from each other) (FIG. 31B), anda second layer of braiding is laid down over the four wire processmandrels the length of the inner polymer tube (FIG. 31C).

Next, the outer polymer tubes are slid over the fully braided innerpolymer tube in the same manner as discussed above, with the exceptionthat a barrier is disposed over a region of the braided inner polymertube to which the pullwires 108 will eventually be anchored (FIG. 31D).In the illustrated embodiment, the barrier is a cylindrical, and inparticular, takes the form of a short section of heat shrink tubing thatis disposed over a corresponding short cylindrical region of the braidedinner polymer tube. Additional heat shrinking (not shown) is thendisposed over the outer polymer tubes and barrier, and the assembly isthen heated to a temperature above the melting temperature of the outertube tubes, but below the melting temperature of the heat shrink tubingand barrier.

As a result, the outer polymer tubes are laminated to the assembly. Inparticular, the outer polymer tubes melt and flow, while the heat shrinktubing shrinks and compresses the melted polymer tubes into the braidand around the four stainless steel process mandrels. Because thebarrier has a melting temperature above the temperature of the appliedheat, the barrier does not melt and prevents the melted outer polymertubes from being compressed into the circumferential region of thebraid. The assembly then cools and solidifies to integrate the innerpolymer tube, braid, and outer polymer tubes together. The barrier isthen removed from the catheter body 102, thereby exposing thecircumferential region of the braid (FIG. 31E). The center copper wire(not shown) can then be pulled from the assembly to create the workinglumen 104, and the four stainless steel wires can be pulled from theassembly to respectively create the four pullwire lumens 110 in the samemanner discussed above (FIG. 31F). The proximal shaft section 120 andtransition section 136 are then fabricated with the distal articulatingsection 114 in the same manner described above.

Then, the proximal ends of the pullwires 108 are inserted into thepullwire lumens 110 at the distal end of the catheter body 102, andadvanced through the lumens 110 until they exit the proximal end of thecatheter body 102 and the distal ends of the pullwires 108 are disposedwithin the exposed circumferential region of the braid (FIG. 31G). Thedistal ends of the pullwires 108 are then anchored to the exposedcircumferential region of the braid via, e.g., soldering, welding,brazing, or gluing (FIG. 31H). In the case where the distal ends of thepullwires 108 are anchored via soldering, 80/20 Au/Sn, which has amelting temperature below the temperature required to damage adjacentcomponents, namely the inner PTFE polymer tube and the stainless steelbraid, can be used. Because the distal ends of the pullwires 108 areanchored between the two layers of braid by virtue of the disposition ofthe pullwire lumens 110 between the two layers of braid, the distal endsof the pullwires 108 are more firmly anchored to the braid, since thebonding material anchored the pullwires 108 above and below thepullwires 108. In contrast, if the pullwires 108 are anchored only toone side of the braid, the pullwires 108 would tend to pull away fromthe braid by either pushing toward the inner polymer tube or beingforced outwardly from the inner polymer tube.

Once the distal ends of the pullwires 108 are anchored to the braid, anouter polymer tube (e.g., a Pebax® 35D extrusion) can then be slid overthe exposed circumferential region of the braid, and then heat shrinktubing (not shown) is slid over the outer polymer tube (FIG. 31I). Theassembly is then heated to a temperature above the melting temperatureof the outer polymer tube, but below the melting temperature of the heatshrink tubing. As a result, the outer polymer tube melts and flows,while the heat shrink tubing shrinks and compresses the melted polymertube into the circumferential portion of the braid. The assembly thencools and solidifies. The proximal end of the catheter tube 102 can thenbe mounted to the proximal adapter 100, and the proximal ends of thepullwires 108 can be installed on the spools or drums 103 of theproximal adapter 101.

It should be appreciated the technique of directly anchoring the distalends of the wires to the braid eliminates the need for the control ring,thereby reducing the cost and fabrication process time for the catheter100. Furthermore, the resulting catheter has a less abrupt stiffnesscharacteristic. Although, the technique of directly anchoring the distalends of wires to the braid has been disclosed in the context ofpullwires, it should be appreciated that this technique can be performedin the context of other types of wires. For example, the wires can beelectrical signal wires and/or radio frequency (RF) ablation wires in anelectrophysiology catheter. In this case, an electrode, rather than anouter polymer tube, can be disposed over the exposed portion of thebraid in electrical communication with the wire or wires. The electrodecan be used as a conductive surface that either measures a localizedelectrical potential or delivers RF ablation energy. In the case wherethe distal end of the wire or wires are soldered to the braid, theelectrode can, e.g., be formed by flowing solder into and over theexposed portion of the braid during the same procedure used to solderthe distal end of the wire or wires to the braid.

With reference now to FIG. 13, an embodiment of another flexible andsteerable elongate catheter 200 will be described. The catheter 200 issimilar to the previously described catheter 100, with the exceptionthat the catheter 200 is designed with three, instead of four pullwires.The catheter 200 may be used in the robotic catheter assembly 18illustrated in FIGS. 5 and 6.

The catheter 200 generally includes an elongate catheter body 202, aworking lumen 204 disposed through the entire length of the catheterbody 202 for delivering one or more instruments or tools from theproximal end of the catheter body 202 to the distal end of the catheterbody 202, a control ring 206 secured the distal end of the catheter body202, a plurality of pullwires 208 housed within one or more lumens 210extending through the catheter body 202, and a proximal adapter 151(with associated spools or drums 153 to which the proximal ends of thepullwires 208 are coupled). The working lumen 204, control ring 206,pullwires 208, and pullwire lumens 210 may be constructed and functionin a similar manner as the working lumen 104, control ring 106,pullwires 108, and pullwire lumens 110 described above.

Like the catheter 100, the catheter 200 is functionally divided intofour sections: a distal tip 212, a distal articulating section 214, atransition section 216, and a proximal shaft section 220.

The distal tip 212, distal articulating section 214, proximal shaftsection 220, and proximal adapter 151 may be respectively identical tothe distal tip 112, distal articulating section 114, proximal shaftsection 120, and proximal adapter 103 of the catheter 100, with theexception that three pullwires 208, instead of three, are accommodated.Thus, three pullwire lumens 210, and thus three pullwires 208, areequally spaced in an arcuate manner (i.e., one hundred twenty degreesapart) within the distal articulating section 214, and the stiffeningtube 230 within the proximal shaft section 220 houses the threepullwires 208. The proximal adapter 201 includes three spools or drums153 to which the proximal ends of the pullwires 208 terminate.

Like the transition section 116, the transition section 216 transitionsthe equal spacing of the lumens 210 in the distal articulating section214 to a single stiffening tube 230 within the proximal shaft section214. With further reference to FIGS. 14-16, the illustrated embodimentaccomplishes this by using an adapter 238, which may be mounted withinthe outer polymer tube of the transition body section 220. The adapter238 is similar to the adapter 138 of the catheter 100, with theexception that it is designed to transition three, instead of four,pullwires 208.

In particular, the adapter 238 includes an adapter body 240 having aproximal end 242 that interfaces with the stiffening tube 230 in theproximal shaft section 220, and a distal end 244 that interfaces withthe three pullwire lumens 210 in the distal articulating section 214.The adapter body 240 may be composed of a suitable rigid material, suchas stainless steel. The adapter 238 further includes a plurality ofchannels 246 formed in the external surface of the adapter body 240, anda single channel 248 formed in the external surface of the adapter body240 in communication with the plurality of channels 246. The distal endsof the channels 246 are equally spaced from each other in coincidencewith the equally spaced lumens 210 in the distal articulating section214, and the proximal end of the single channel 248 is in coincidencewith the stiffening tube 230 in the proximal shaft section 220. One ofthe channels 246 linearly extends along the length of the adapter body240, while the remaining two channels 246 spirals around the length ofthe adapter body 240, so that the proximal ends of all three channels246 converge into the single channel 248. Thus, the three pullwires 208extend proximally from the distal articulating section 214, along thethree channels 246, converge into the single channel 248, and then intothe stiffening tube 230.

The adapter 238 further includes a working lumen 254 extending entirelythrough the adapter body 240. The distal end of the working lumen 254 isin coincidence with the portion of the working lumen 204 extendingthrough the distal articulating section 214, and the proximal end of theworking lumen 254 is in coincident with the portion of the working lumen204 extending through the proximal shaft section 220. In the same mannerthat the working lumen 204 and stiffening tube 230 are offset from theaxis of the proximal shaft section 120, the working lumen 254 and singlechannel 248 are offset from the axis of the adapter body 240. Like withthe adapter 138 of the catheter 100, the adapter 238 allows the threepullwires 208 to be transitioned from the respective lumens 210 of thedistal articulating section 214 into the single stiffening tube 230 ofthe proximal shaft section 220 without having to spiral the pullwires208 and corresponding lumens through the wall of the catheter tube 202,thereby allowing the thickness of the wall to be uniform and minimizingthe possibility of weakened regions in the catheter tube 202 andpossible inadvertent kinking.

With reference now to FIG. 17, an embodiment of another flexible andsteerable elongate catheter 300 will be described. The catheter 300 issimilar to the previously described catheter 100, with the exceptionthat the catheter 300 is designed as a rapid exchange catheter, which isfacilitated by the placement of the pullwires on one arcuate side of theproximal shaft section, and in particular, within the stiffening tube.The catheter 300 may be used in a robotic catheter assembly 358, whichis similar to the robotic catheter assembly 18 illustrated in FIGS. 5and 6, with the exception that the robotic catheter assembly 358includes a guidewire manipulator 360 that is in a side-by-sidearrangement with a leader catheter manipulator 362, as shown in FIG. 18,which is facilitated by the rapid exchange architecture of the catheter300.

The design of the catheter 300 applies to a leader catheter of atelescoping catheter pair; e.g., a leader catheter 300 and outer guidesheath 36. With a pair of telescoping catheters, the therapy willusually be delivered through the outer catheter after the inner catheterhas been removed. Therefore, the inner catheter does not need to have alumen extending through its center the entire length of its shaft. Thepurpose of the outer catheter is to facilitate access to the site ofinterest and then to provide a stable, controllable (steerable) lumen todeliver a therapeutic device. Therefore, the outer catheter needs tohave a lumen through the center the entire length of its shaft. Thepurpose of the inner catheter is to work in conjunction with the outercatheter and guide wire in a telescoping motion to inchworm the cathetersystem through the anatomy. This can be achieved by just having a shortsection at the distal end of the leader catheter supporting the guidewire, and allowing the remainder of the wire to run parallel to theleader catheter.

The catheter 300 generally includes an elongate catheter body 302, aworking lumen 304 disposed through the entire length of the catheterbody 302 for delivering one or more instruments or tools from theproximal end of the catheter body 302 to the distal end of the catheterbody 302 a control ring 306 secured the distal end of the catheter body302, a plurality of pullwires 308 housed within one or more lumens 310extending through the catheter body 302, and a proximal adapter 301(with associated spools or drums 303 to which the proximal ends of thepullwires 308 are coupled). The working lumen 304, control ring 306,pullwires 308, and pullwire lumens 310, and proximal adapter 301 may beconstructed and function in a similar manner as the working lumen 104,control ring 106, pullwires 108, pullwire lumens 110, and proximaladapter 101 described above.

Like the catheter 100, the catheter 300 is functionally divided intofour sections: a distal tip 312, a distal articulating section 314, aproximal shaft section 320, and a transition section 316. The distal tip312 and distal articulating section 314 of the catheter 300 may beidentical to the distal tip 112 and distal articulating section 114 ofthe catheter 100. The transition section 318 of the catheter 300 isidentical to the transition section 116 of the catheter 100 with theexception that the transition section 316 includes a rapid exchange port322 that is in communication with a guidewire lumen 304. The exactlocation of the rapid exchange port 322 relative to the distal tip ofthe catheter 300 can vary by varying the length of the distalarticulating section 314 and transition section 316. Ultimately, thelocation of the rapid exchange port 322 will depend on the requireddistance that the catheter 300 needs to extend beyond the distal tip ofthe outer guide sheath 36. However, the rapid exchange port 322 shouldnever exit the distal tip of the outer guide sheath 36—else it would bedifficult to retract the distal end of the catheter 300 back into theouter guide sheath 36. Thus, the length of the over-the-wire segment ofthe catheter 300 (i.e., the total length of the distal tip 312, distalarticulating section 314, and transition section 316) should always begreater than the maximum extension of the catheter 300 from the outerguide sheath 36. A shorter the over-the-wire segment length, however,will be easier and faster to use, because the robot may control more ofthe insertion and withdrawal of the catheter 300.

The proximal end of transition section 316 is tapered to provide asmooth rapid exchange port 322. This allows the guide wire 40 to befront-loaded through the proximal end of the outer guide sheath 36 andthen exit out through the exit port (not shown) at the distal tip 312 ofthe catheter 300. The proximal shaft section 320 of the catheter 300 iscomposed of a stiffening tube 330, which is in communication with thepullwire lumens 310 via the transition section 316 (e.g., via use of theadapter 138 illustrated in FIGS. 8 and 9).

Thus, when the catheter 300 is used with the outer guide sheath 36, theguide wire 40 will travel outside the catheter 300 within the outerguide sheath 36, until it enters the rapid exchange port 322, and thenthrough the guide wire lumen 304, and then out through the guide wireexit port. Thus, the catheter 300 and the guide wire 40 will travelparallel to each other through the outer guide sheath 36 until the guidewire 40 enters the rapid exchange port 322, after which they travelconcentrically relative to each other. In addition, contrast agents canalso be injected through a flush port (not shown) at the proximal end ofthe outer guide sheath 36, which may enter the rapid exchange port 322,and exit out the guide wire exit port.

The design of the rapid exchange leader catheter 300 allows forsignificantly greater robotic control of position. In particular,because the catheter 300 and guide wire 40 are not concentricallyarranged relative to each other, but instead are two independentdevices, at the proximal end of the assembly, greater independentrobotic control is enabled without the need for an excessively longinstrument driver. That is, the guidewire manipulator 360 can now beplaced in a side-by-side arrangement with the leader cathetermanipulator 362. The instrument driver has separate drive trains for thecatheter 300 and guide wire 40, allowing the user to have fullindependent insertion and withdrawal control of both the catheter 300and the guide wire 40 at all times. This results in less fluoroscopictime and radiation exposure, faster procedure time, greater length ofrobotic insertion and retraction of the catheter 300 and guide wire 40,less risk of losing guide wire position, less risk of breaching thesterile field, and allows for use of shorter guide wires and thereforeone less person in the sterile field.

It should be appreciated that this rapid exchange design is applicableto other non-steerable catheters (e.g., atherectomy devices or graspers)that require the routing of wires from the proximal end to an operativeelement at the distal end of the catheter. The method of manufacturingthe catheter 100 may be similar to the method of manufacturing thecatheter 300 described above, with the exception that the proximal endof the transition section 316 is tapered, and the stiffening tube 330forms the entirety of the catheter proximal shaft section 320 and issuitably bonded within the proximal end of the transition section 316.

One method of using the robotic catheter assembly 358 illustrated inFIG. 18 to access a diseased site within the vasculature of a patientwill now be described. First, an incision in a blood vessel of thepatient (e.g., a femoral artery) is made using a conventionaltechniques, and a starter wire is advanced into the artery. Next, theleader catheter 300 is preloaded into the outer guide sheath 36,ensuring that the rapid exchange port 322 remains inside the outer guidesheath 36. Then, the guide wire 40 is backloaded into the tip of theleader catheter 300. When the guide wire 40 exists the rapid exchangeport 322, the guide wire 40 is advanced through the outer guide sheath36 next to the leader catheter 300 until it exits at the back of theproximal adapter 48 of the outer guide sheath 36. Next, the guide wire40 is held in a fixed position, while the leader catheter 300 isadvanced several centimeters into the femoral artery over the guide wire40. Then, the proximal adapter 301 of the leader catheter 300 and guidewire 40 are loaded onto the robotic instrument driver 34.

Then, the guide wire 40 and leader catheter 300 can be roboticallydriven remotely to the site of interest using the operator controlstation 16. If a selective angiogram is required when driving the guidewire 40 and leader catheter 300, a contrast agent may be injectedthrough an injection port on the outer guide sheath 36. If the guidewire 40 is 0.035″ in diameter and occupies most of the available spacethrough the leader catheter, almost all of the contrast agent will exitthe distal tip of the outer guide sheath 36. In contrast, if guide wire40 is 0.018″ in diameter, some of the contrast agent will exit out thedistal tip of the leader catheter 300, and some of the contrast agentwill exit out the distal tip of the outer guide sheath 36. Either way,the physician will be capable of obtaining a selective angiogram for thevessel of interest.

Once the guide wire 40 is at the site of interest, the physician maythen robotically withdraw the leader catheter 300 until the“over-the-wire” section exits at the back of the proximal adapter 48 ofthe outer guide sheath 36. This can be accomplished without the use offluoroscopy, since the robotic catheter system 358 will ensure that theposition of the guide wire 40 relative to the patient is maintained.Depending on the robotic configuration used (i.e., the travel distanceof the leader catheter carriage), this leader catheter 300 removal stepmay be accomplished entirely remotely or part manually and partrobotically.

The physician may then manually remove the guide wire 40 from the guidewire manipulator 360, slide out the last few inches of the leadercatheter 300 under fluoroscopy, and remove leader catheter 300 from thepatient. A therapeutic device may then be manually delivered through theouter guide sheath 36. If the therapeutic device is itself a rapidexchange catheter, after the “over-the-wire” section has been manuallypassed into the outer guide sheath 36, the guide wire 40 may then bepositioned back onto the guide wire manipulator 30, and the robot can beused to hold the position of the guide wire 40 while the therapeuticdevice is manually advanced. If the leader catheter 300 needs to bereinstalled to access another site of interest within the patient, itmay be backloaded over the guide wire 40 until the guide wire 40 exitsthe rapid exchange port 322. The guide wire 40 may then be loaded ontothe guide wire manipulator 360 and the leader catheter 300 isreinstalled on the instrument driver 34. The guide wire 40 and leadercatheter 300 can then be robotically driven remotely to the new site ofinterest using the operator control station 16.

With reference now to FIG. 19, an embodiment of yet another flexible andsteerable elongate catheter 400 will be described. The catheter 400 issimilar to the previously described catheter 100, with the exceptionthat the catheter 400 has multiple regions of articulation, and inparticular, a distal region of articulation and a proximal region ofarticulation. The catheter 400 enables two regions of articulation byaltering the axial stiffness, flexural stiffness, and torsionalstiffness of the catheter body in very specific locations. The catheter400 may be used in the robotic catheter assembly 18 illustrated in FIGS.5 and 6.

The catheter 400 generally includes an elongate catheter body 402, whichlike the catheter body 102, may be comprised of multiple layers ofmaterials and/or multiple tube structures that exhibit a low bendingstiffness, while providing a high axial stiffness along the neutralaxis. Also like the catheter 100, the catheter 400 further includes aworking lumen 404 disposed through the entire length of the catheterbody 402 for delivering one or more instruments or tools from theproximal end of the catheter body 402 to the distal end of the catheterbody 402, a control ring 406 secured the distal end of the catheter body402, a plurality of pullwires 408 housed within one or more lumens 410extending through the catheter body 402, and a proximal adapter 401(with associated spools or drums 403 to which the proximal ends of thepullwires 408 are coupled). The working lumen 404, control ring 406,pullwires 408, pullwire lumens 410, and proximal adapter 401 may beconstructed and function in a similar manner as the working lumen 104,control ring 106, pullwires 108, pullwire lumens 110, and proximaladapter 101 described above.

The catheter 400 is functionally divided into five sections: a distaltip 412, a distal articulating section 414, a transition section 416, aproximal articulating section 418, and a proximal shaft section 420.

The distal tip 412 includes an atraumatic rounded tip portion 422, acontrol portion 424 in which the control ring 406 is mounted, and anexit port (not shown) in communication with the working lumen 404 andfrom which a working catheter or guidewire may extend distallytherefrom. The distal tip 412 may be constructed and function in asimilar manner as the distal tip 112 described above.

Like the distal articulating section 114, four pullwire lumens 410 areequally spaced in an arcuate manner (i.e., ninety degrees apart) withinthe distal articulating section 414 to allow the distal articulatingsection 414 to be articulated in an infinite number of directions withinthe same plane (effectively, providing two degrees of freedom: pitch androll). In an alternative embodiment, another number of pullwires lumens410, and thus, pullwires 408, can be used. For example, three pullwirelumens 410 can be equally spaced in an arcuate manner (i.e., one hundredtwenty degrees apart). The distal articulating section 414 preferablyallows for a moderate degree of axial compression and optimal lateralflexibility. The distal articulating section 414 includes a rigidportion 426 and an articulatable portion 428. The distal articulatingsection 414 may be constructed and function in a similar manner as thedistal articulating section 114 described above, with the pullwirelumens 410 extending through the rigid portion 426 and articulatableportion 428 as unsupported cavities in which the four pullwires 408 arerespectively disposed.

The transition section 416 transitions the equal spacing of the lumens410 in the distal articulating section 414 too close spacing of thelumens 410 in the proximal articulating section 418. Instead of using anadapter 138, as illustrated in FIGS. 8 and 9, the lumens 410 in thetransition section 416 are gradually displaced about the axis of thecatheter body 402 within the wall of the transition section 416. Inparticular, the one lumen 410 that is on the same side as the closelyspaced lumens 410 in the proximal articulating section 418 may extendlinearly along the length of the transition section 416, while theremaining three lumens spiral around the length of the transitionsection 416 until they converge onto the same side of the proximalarticulating section 418. The transition section 416 is more rigid thanthe distal articulating section 414 to allow the distal articulatingsection 414 to bend about the transition section 416.

The transition section 416 resists axial compression to clearly definethe proximal end of the distal articulating section 414 and transfer themotion of the pullwires 408 to the distal articulating section 414,while maintaining lateral flexibility to allow the catheter 400 to trackover tortuous anatomies. In one embodiment, the transition section 416is 33 mm in length. The pullwire lumens 410 extending through thetransition section 416 take the form of 0.007″×0.009″ polyimide tubescircumferentially oriented relative to each other by ninety degrees, andthus, can be considered stiffening members in which the pullwires 408are respectively disposed. The entire working lumen 404 within thetransition section 416 is formed by an inner polymer tube (e.g., 0.001″thick PTFE). The transition section 416 has a several portions ofdiffering rigidities formed by having different polymer outer tubes. Inone embodiment, the transition section 416 includes a 1 mm pullwirelumen anchoring portion 430 having a relatively rigid outer polymer tube(e.g., Nylon-12) that increases the support for holding the distal endsof the polyimide pullwire lumens 410. The transition section 416 furtherincludes a 4 mm flexible portion 432 having a relatively flexible outerpolymer tube (e.g., Pebax® 40D) that transitions from the relativelyflexible distal section 314 to a 28 mm stiff portion 434 having arelatively stiff outer polymer tube (e.g., Pebax® 55D).

To increase its axial rigidity, the transition section 416 comprises adouble braided layer (e.g., sixteen 0.0005″×0.003″ spring temper 304Vstainless steel wires braided at 140 ppi in a 2 over 2 pattern) embeddedwithin the outer polymer tubes of all three of the anchoring portion430, flexible portion 432, and rigid portion 434. Three of the polyimidepullwire lumens 410 spiral around the stiff portion 434 of thetransition section 416, which along with the remaining polyimidepullwire lumen 410, converge to the same side of the catheter body 402.

The proximal articulating section 418 significantly allows for amoderate degree of axial compression and optimal lateral flexibility.The pullwire lumens 410 are grouped on one arcuate side of the proximalarticulating section 418 to allow it to be articulated in one direction.Preferably, the pullwire lumens 410 are grouped in a manner that locatestheir centers within an arcuate angle relative to the geometriccross-sectional center of the proximal shaft section of less than onehundred eighty degrees, and more preferably, less than ninety degrees,and most preferably, less than forty-five degrees.

In one embodiment, the proximal articulating section 418 is 16 mm inlength. Preferably, the proximal articulating section 418 is more rigidthan the distal articulating section 414, such that independent controlof the distal articulating section 414 and the proximal articulatingsection 418 can be achieved, as discussed in further detail below. Likein the transition section 416, the pullwire lumens 410 extending throughthe proximal articulating section 418 take the form of 0.007″×0.009″polyimide tubes, and thus, can be considered stiffening members in whichthe pullwires 408 are respectively disposed. The entire working lumen404 within the proximal articulating section 418 comprises an innerpolymer tube (e.g., 0.001″ thick PTFE). The proximal articulatingsection 418 has two portions of differing rigidities formed by havingdifferent polymer outer tubes. In one embodiment, the proximalarticulating section 418 includes a 15 mm articulatable portion 436having a relatively flexible outer polymer tube (e.g., Pebax® 40D) and a1 mm pullwire lumen anchoring portion 438 having a relatively rigidpolymer tube (e.g., Nylon) that increases the support for holding thepolyimide pullwire lumens 410. To increase its axial rigidity andelastic properties, the proximal articulating section 418 comprises adouble braided layer (e.g., sixteen 0.0005″×0.003″ spring temper 304Vstainless steel wires braided at 140 ppi in a 2 over 2 pattern) embeddedwithin the outer polymer tubes.

The proximal shaft section 420 resists axial compression to clearlydefine the proximal end of the proximal articulating section 418 andtransfer the motion of the pullwires 408 to the proximal articulatingsection 314, while maintaining lateral flexibility to allow the catheter400 to track over tortuous anatomies. Like with the proximalarticulating section 314, the pullwire lumens 410 are grouped on onearcuate side of the proximal shaft section 420. Because the pullwirelumens 410 are more rigid than the remaining material of the proximalarticulating section 418 (i.e., the pullwire lumens 410 are composed ofa polyimide, whereas the remaining portion of the proximal articulatingsection 418 is composed of a low durometer polymer composite), theneutral axis will be shifted closer to the axis of the grouping ofpullwire lumens 410, thereby providing the aforementioned advantagesdiscussed above with respect to the catheter 100.

The proximal shaft section 420 represents the majority of the length ofthe catheter 400, and gradually transitions the catheter 400 from themore flexible proximal articulating section 418 to the more rigidremaining portion of the catheter 400. For example, the proximal shaftsection 420 may include three proximal portions 440, 442, 444 thatincrease in rigidity in the proximal direction. The proximal shaftsection 420 may be constructed and function in a similar manner as theproximal shaft section 120 described above.

Having described its function and construction, one method ofmanufacturing the catheter 400 will now be described. Like the method ofmanufacturing the catheter 100, in this method, the distal articulatingsection 414 and the combined proximal articulating section 418/proximalshaft section 420 are fabricated separately, and then mounted to eachother when the transition section 416 is fabricated. The distal tip 412can then be formed onto the assembly to complete the catheter 400.

The distal articulating section 414 can be fabricated in the same manneras the distal articulating section 114 described above. The proximalarticulating section 418 and proximal shaft section 420 are fabricatedtogether by first inserting a copper wire process mandrel through alumen of an inner polymer tube (e.g., a PTFE extrusion) having theintended length of the combined proximal articulating section418/proximal shaft section 420. Then, using a conventional braidingmachine, a first layer of braiding is laid down over the length of theinner polymer tube. Next, four PTFE-coated stainless steel wire processmandrels with polyimide tubing are respectively disposed over the lengthof the braided inner polymer tube in a group on one side of the innerpolymer tube, and a second layer of braiding is laid down over the fourwire process mandrels the length of the inner polymer tube. Next, outerpolymer tubes having different durometers and lengths corresponding tothe lengths of the different portions of the proximal articulatingsection 418 and the proximal shaft section 420 (e.g., a Pebax® 40Dextrusion for the articulatable portion 436 and a Nylon-12 extrusion forthe anchoring portion 438 of the proximal articulating section 418, andPebax® 55D, Pebax® 72D, and Nylon-12 extrusions for the respectiveproximal portions 440, 442, 444 of the proximal shaft section 420) areslid over the fully braided inner polymer tube, and then heat shrinktubing is slid over the outer polymer tubes.

The assembly is then heated to a temperature above the meltingtemperature of the outer polymer tubes, but below the meltingtemperature of the heat shrink tubing. As a result, the outer polymertubes melt and flows, while the heat shrink tubing shrinks andcompresses the melted outer polymer tubes into the braid and around thefour stainless steel process mandrels. The assembly then cools andsolidifies to integrate the inner polymer tube, braid, and outer polymertubes together. Then, the center copper wire can be pulled from theassembly to create the working lumen 404, and the four stainless steelwires can be pulled from the assembly, thereby leaving the polyimidetubing with the assembly to respectively create the four pullwire lumens410.

Next, the distal articulating section 414 and the combined proximalarticulating section 418/proximal shaft section 420 are coupled to eachother by fabricating the transition section 416 between the distalarticulating section 414 and the combined proximal articulating section418/proximal shaft section 420. In particular, the transition section416 is partially fabricated by first inserting a PTFE-coated copper wireprocess mandrel through a lumen of an inner polymer tube (e.g., a PTFEextrusion) having the intended length of the transition section 416.Then, using a conventional braiding machine, a first layer of braidingis laid down over the length of the inner polymer tube. Then, each offour PTFE-coated stainless steel wire process mandrels is insertedthrough a lumen of a polyimide tube having the intended length of thetransition section 416. The linear length of one of these wire processmandrels will equal the length of the transition section 416, while thelinear lengths of the remaining three wire process mandrels will beslightly greater than the length of the transition section 416 tocompensate for the additional length required to spiral these wireprocess mandrels around the transition section 416.

Next, the opposing ends of the center wire process mandrel arerespectively inserted through the working lumens 404 of the distalarticulating section 414 and the combined proximal articulating section418/proximal shaft section 420, and the opposing ends of four wireprocess mandrels are inserted through the pullwire lumens 410 of thedistal articulating section 414 and the pullwire lumens 410 of thecombined proximal articulating section 418/proximal shaft section 420.The distal articulating section 414 and the combined proximalarticulating section 418/proximal shaft section 420 are then slidtogether until the inner polymer tube of the transition section 416abuts the inner polymer tubes of the distal articulating section 414 andthe proximal articulating section 418, and the polyimide tubing on thefour wire process mandrels abuts the pullwire lumens 410 of the distalarticulating section 414 and the pullwire lumens 410 of the proximalarticulating section 418. Three of the wire process mandrels are thenspiraled around and bonded to the inner polymer tube, and a second layerof braiding is laid down over the four wire process mandrels the lengthof the inner polymer tube.

Next, outer polymer tubes having different durometers and lengthscorresponding to the lengths of the different portions of the transitionsection 416 (e.g., a Nylon-12 extrusion for the anchoring portion 430, aPebax® 40D extrusion for the flexible portion 432, and a Pebax® 55Dextrusion for the rigid portion 434) are slid over the fully braidedinner polymer tube, and then heat shrink tubing is slid over the outerpolymer tubes. The assembly is then heated to a temperature above themelting temperature of the outer polymer tubes, but below the meltingtemperature of the heat shrink tubing. As a result, the outer polymertubes melt and flows, while the heat shrink tubing shrinks andcompresses the melted outer polymer tubes into the braid and around thefour stainless steel process mandrels. The assembly then cools andsolidifies to integrate the inner polymer tube, braid, and outer polymertubes together. Then, the center copper wire can be pulled from theassembly to create the working lumen 404 within the transition section416, and the four stainless steel wires can be pulled from the assembly,thereby leaving the polyimide tubing within the assembly to respectivelycreate the four pullwire lumens 410 within the transition section 416.

The control ring 406, pullwires 408, and distal tip 412 may be installedon the assembly in the same manner as the control ring 106, pullwires108, and distal tip 112 described above. Alternatively, in a similarmanner discussed above, instead of utilizing a control ring 106, thedistal ends of the pullwires 108 may be attached directly to a sectionor portion of the catheter body 102 where it may be steered,articulated, or bent, and in this case, to the distal end of the distalarticulating section 414.

Significantly, the catheter 400 may be operated in a manner thatindependently controls the articulation of the distal articulatingsection 414 and proximal articulating section 418. The theory behind thedesign of the catheter 400 is that if only one pullwire 408 istensioned, only the distal articulating section 414 will bend. If allfour pullwires 408 are uniformly tensioned (common mode), then only theproximal articulating section 418 will bend. Any variation in wiretension from these two scenarios will result in the bending of both thedistal articulating section 414 and proximal articulating section 418assuming at least two of the pullwires 408 are tensioned. Effectively,the distal articulating section 414 provides the catheter 400 with twodegrees of freedom (bend and roll), and the proximal articulatingsection 418 provides the catheter 400 with one degree of freedom (bend).

In particular, when two or less of the pullwires 408 are tensioned atrelatively small amount, the distal articulating section 414 articulatesin the direction of the tensioned pullwire(s) 310. Because the proximalarticulating section 418 is designed to be more laterally rigid than thedistal articulating section 414, the net moment created at the distaltip 412 nominally articulates only the distal articulating section 414,but is not sufficient to overcome the lateral stiffness of the proximalarticulating section 418 in a manner that would cause a significant bendin the proximal articulating section 418. This feature thereforefacilitates independent articulation of the distal articulating section414 relative to the proximal articulating section 418 even through thepullwires used to articulate the distal articulating section 414 extendthrough the proximal articulating section 418.

When all four of the pullwires 408 are uniformly tensioned, there willbe no net moment created at the distal tip 412 due to the equal arcuatedistribution of the pullwires 408 at the distal tip 412. As such, thedistal articulating section 414 will not articulate. However, becauseall four of the pullwires 408 are grouped together on one side of theproximal articulating section 418, a net moment is created at the distalend of the proximal articulating section 418. As such, the proximalarticulating section 418 will articulate in the direction of the groupedpullwires 408. This feature therefore facilitates independentarticulation of the proximal articulating section 418 relative to thedistal articulating section 414 even through the pullwires used toarticulate the proximal articulating section 418 extend through thedistal articulating section 414.

When two or less than the pullwires 408 are tensioned a relatively largeamount, and the remaining pullwires 408 are also tensioned but not asmuch as the initially tensioned pullwires 408 are tensioned, then thenet moment is created at the distal tip 412 greatly articulates thedistal articulating section 414 in the direction of the initiallytensioned pullwire(s) 410, while the combined moment created at thedistal end of the proximal articulating section 418 moderatelyarticulates the proximal articulating section 418 in the direction ofthe grouped pullwires 408, thereby causing a large bend in the distalarticulating section 414 while causing a small bend in the proximalarticulating section 418.

When two or less of the pullwires 408 are tensioned a relatively smallamount, then all of the pullwires 408 are uniformly tensioned anadditional amount, a net moment is created at the distal tip 412 tomoderately articulate the distal articulating section 414 in thedirection of the tensioned pullwire(s) 410, while the additionaltensioning of all of the pullwires 408 greatly articulates the proximalarticulating section 418, thereby causing a small bend in the distalarticulating section 414 while causing a large bend in the proximalarticulating section 418.

The computer 28 within the control station 16 may be programmed withalgorithms that take into account the elastic behavior of the distalarticulating section 414 and proximal articulating section 418 andcatheter stiffness when computing the displacements of the pullwires 408required to enable complete and independent control of both the distalarticulating section 414 and proximal articulating section 418.

By achieving independent articulation control over the distalarticulating section 414 and the proximal articulating section 418,anatomical sites of interest can be more easily accessed. The catheter400 can be used to access either the left coronary artery or the rightcoronary artery from the aorta of the patient.

To access the left coronary artery, the pullwire or pullwires 408 in thedirection of the left coronary artery (in this case, pullwire 1) can betensioned to bend the distal articulating section 414 ninety degreestowards the left coronary artery, as illustrated in FIG. 20. Then, allfour of the pullwires 408 can be tensioned an additional amount to bendthe proximal articulating section 418 to seat the distal tip 412 of thecatheter 400 within the ostium of the left coronary artery, as shown inFIG. 21. For example, if the pullwire 1 is initially tensioned at aforce of 7 units to bend the distal articulating section 414, anadditional force of 3 units can be used to tension all four pullwires1-4 (resulting in a 10 unit tension in pullwire 1, and a 3 unit tensionin pullwires 2-4). There is now 19 units of force on the proximalarticulating section 418, which is adequate to bend the proximalarticulating section 418. But there remains a delta of 7 units oftension more on pullwire 1 than on all other wires, and therefore thereis no further bending of the distal articulating section 414.

To access the right coronary artery, the pullwire or pullwires 408 inthe direction of the right coronary artery (in this case, pullwire 4)can be tensioned to bend the distal articulating section 414 ninetydegrees to seat the distal tip 412 within the ostium of the rightcoronary artery, as illustrated in FIG. 22. If the distal tip 412 isseated too deeply within the ostium of the right coronary artery, thenall four of the pullwires 408 can be tensioned an additional amount tobend the proximal articulating section 418 to properly seat the distaltip 412 within the ostium of the right coronary artery, as shown in FIG.23. For example, if the pullwire 4 is initially tensioned at a force of7 units to bend the distal articulating section 414, an additional forceof 1 unit can be used to tension all four pullwires 1-4 (resulting in an8 unit tension in pullwire 1, and a 1 unit tension in pullwires 2-4) toslightly bend the proximal articulating section 418.

As another example, by independently articulating the catheter 400, theleft coronary artery of a patient can be accessed regardless of the typeof anatomy. In particular, FIG. 24A illustrates independent articulationof the proximal articulating section 418 and distal articulating section414 of the catheter 400 to access the left coronary artery in a “normal”anatomy; FIG. 24B illustrates independent articulation of the proximalarticulating section 314 and distal articulating section 418 of thecatheter 400 to access the left coronary artery in a “wide” anatomy; andFIG. 24C illustrates independent articulation of the proximalarticulating section 418 and distal articulating section 414 of thecatheter 400 to access the left coronary artery in an “unfolded”anatomy.

Significantly, by taking advantage of the geometric construction andvariation in catheter flexibility to achieve independent control overmultiple articulation segments, several advantages are achieved usingthe catheter 400. First, repeatable and consistent articulationperformance at two unique locations in the catheter 400 can be achieved.Second, while other dual articulating catheters achieve independentcontrol over multiple articulation segments by employing multiplecontrol rings and having dedicated pullwire or articulation mechanisms,the catheter 400 does not require a second control ring or dedicatedcontrol mechanism to effect a second articulation within the catheter,but rather only utilizes the distal-most control ring and the pullwiresthat are already installed for the distal articulation of the catheter.Thus, by eliminating the need for a second control ring and a separateset of pullwires, few components are needed. Third, the need for aprocedure to fasten a second set of wires to a second control ring iseliminated, thereby decreasing the cost of manufacturing the catheter.Fourth, an existing driver instrument initially designed for a catheterhaving a single region of articulation (e.g., the catheter 100 orcatheter 400) can be utilized for a catheter having dual regions ofarticulation (e.g., the catheter 400), since no additional pullwires areneeded, and thus the proximal adapter of the catheter remains the same.It should also be noted that robotic control of the catheter 400efficiently and quickly manages the tensioning of the pullwires toeffect the articulation of the catheter 400, and therefore, there is noneed for the physician to think about which of the pullwires to tensionand the magnitude of the tension to be placed on the pullwires.

With reference now to FIG. 25, an embodiment of yet another flexible andsteerable elongate catheter 500 will be described. The catheter 500 issimilar to the previously described catheter 400, with the exceptionthat the catheter 400 has a proximal region of articulation thatbi-directionally bends in a plane. The catheter 500 may be used in therobotic catheter assembly 18 illustrated in FIGS. 5 and 6.

The catheter 500 generally includes an elongate catheter body 502 (whichmay have any suitable cross-section, such as circular or rectangular),which like the catheter body 502, may be comprised of multiple layers ofmaterials and/or multiple tube structures that exhibit a low bendingstiffness, while providing a high axial stiffness along the neutralaxis. Also, like the catheter 400, the catheter 500 further includes aworking lumen 504 disposed through the entire length of the catheterbody 502 for delivering one or more instruments or tools from theproximal end of the catheter body 502 to the distal end of the catheterbody 502, a control ring 506 secured the distal end of the catheter body502, a plurality of pullwires 508 housed within one or more lumens 410extending through the catheter body 502, and a proximal adapter 501(with associated spools or drums 503 to which the proximal ends of thepullwires 508 are coupled). The working lumen 504, control ring 506,pullwires 508, pullwire lumens 510, and proximal adapter 501 may beconstructed and function in a similar manner as the working lumen 404,control ring 406, pullwires 408, pullwire lumens 410, and proximaladapter 401.

The working lumen 504, control ring 506, pullwires 508, and pullwirelumens 510 may be constructed and function in a similar manner as theworking lumen 404, control ring 406, pullwires 408, and pullwire lumens410 described above, except that one of the pullwires 508 is used toprovide proximal bi-directional articulation.

In particular, as previously stated, tensioning one or more of thepullwires 408 in the catheter 400 may cause the proximal articulatingsection 418 to bend somewhat. Such proximal bend can be increased byuniformly increasing the tension in the pullwires 408, but cannot bedecreased. Thus, the proximal articulating section 418 can only bend ina single direction (i.e., in the direction of the grouped pullwires408).

In contrast, the catheter 500 utilizes a counteracting pullwire 508′that circumferentially opposes the group of pullwires 508 in theproximal articulating section, such that tensioning the counteractingpullwire 508 bends the proximal articulating section in one direction,while uniformly tensioning the three remaining pullwires 508 bends theproximal articulating section in an opposite direction. Notably, anexisting driver instrument initially designed for a catheter having fourpullwires for a single region of articulation (e.g., the catheters 100,200, and 300) or a distal region of articulation and a proximal regionof uni-directional articulation (e.g., the catheter 400) can be utilizedfor a catheter having a distal region of articulation (using 3 of thepullwires) and a proximal region of bi-directional articulation with theremaining wire (e.g., the catheter 500), since no additional pullwiresare needed, and thus the proximal adapter of the catheter remains thesame.

The catheter 500 is functionally divided into five sections: a distaltip 512, a distal articulating section 514, a transition section 516, aproximal articulating section 518, and a proximal shaft section 520.

The distal tip 512 is identical to the distal tip 412, and the distalarticulating section 514 is identical to the distal articulating section414 of the catheter 400, with the exception that three pullwire lumens510 (rather than four), and thus, three pullwires 508, are equallyspaced in an arcuate manner (i.e., one hundred twenty degrees apart)within the distal articulating section 514 to allow it to be articulatedin an infinite number of directions within the same plane (effectively,providing two degrees of freedom: bend and roll).

The transition section 516 is identical to the transition section 416 ofthe catheter 400, with the exception that the distal end of thecounteracting pullwire 508′ is anchored within the proximal end of thetransition section 516, and the three remaining pullwire lumens 510 andassociated pullwires 508 are equally spaced in an arcuate manner (i.e.,one hundred twenty degrees apart).

The proximal articulating section 518 is identical to the proximalarticulating section 418 of the catheter 500, with the exception thatthe counteracting pullwire 508′ is oriented one hundred eighty degreesfrom the group of the remaining three pullwires 508, and thecounteracting pullwire lumen 510′ in which the counteracting pullwire508′ is disposed takes the form of an unsupported cavity. The proximalshaft section 520 is identical to the proximal shaft section 420 of thecatheter 400, which has the feature of shifting the neutral axis closerto the axis of the grouping of pullwire lumens 510, thereby providingthe aforementioned advantages discussed above with respect to thecatheter 100.

The method of manufacturing the catheter 500 is the same as the methodof manufacturing the catheter 500 described above, with the exceptionthat the distal end of the counteracting pullwire 508′ is anchoredwithin the pullwire lumen 510′ in the proximal end of the transitionsection 516, and the pullwire lumen 510′ is unsupported through thetransition section 516 and the proximal articulating section 518 untilit reaches the distal end of the proximal shaft section 520, at whichpoint it is composed of a polyimide tube that is grouped with theremaining three polyimide lumens 510. The counteracting pullwire 508′may be anchored in the proximal end of the transition section 516 byusing another control ring or anchoring it directly to braid.

Like with the catheter 500, the computer 28 within the control station16 (shown in FIG. 4) may be programmed with algorithms that take intoaccount the elastic behavior of the distal articulating section 514 andproximal articulating section 518 and catheter stiffness when computingthe displacements of the pullwires 508 required to enable complete andindependent control of both the distal articulating section 514 andproximal articulating section 518. To fully utilize the multi-bendarchitecture of the catheter 500, it is important for the physician toindependently control the distal articulating section 514 and proximalarticulating section 518. However, because the any distal moment createdat the distal tip 512 of the catheter 500 will cause bending of theproximal articulating section 518 as small as it may be, the computer 28employs a multi-bend control algorithm that takes into account theinadvertent bending of the proximal articulating section 518 in order toensure full independent articulation of the distal articulating section514 and the proximal articulating section 518. Ideally, when onlybending of the distal articulating section 514 is desired, the proximalarticulating section 518 should not bend, and when only bending of theproximal articulating section 518 is desired, the distal articulatingsection 514 should not bend.

With reference to FIG. 26, a multi-bend segment of the catheter 500 isshown having a distal articulation angle α_(d) and a proximalarticulation angle α_(p). The multi-bend segment of the catheter alsohas a distal articulation roll e. Thus, the catheter 500 has twoarticulation Degrees of Freedom (DOFs) in the distal bend and a singlearticulation DOF in the proximal bend. From a controls perspective, thetransition section 516 of the catheter 500 couples the distalarticulating section 514 and the proximal articulating section 518 insuch a way that the coupling can be counteracted by the counteractingpullwire 508′. The multi-bend control algorithm employed by the computer28 utilizes this configuration to independently control the bends in thedistal articulating section 514 and the proximal articulating section518.

The following relation can be used to calculate the number ofindependently controllable DOFs (m) in a catheter based on the number ofpullwires (n):m≦n−1  [1]

Thus, the four pullwires 508 of the catheter 500 can be used toindependently control three DOFs, in particular, the distal articulationangle α_(d), proximal articulation angle α_(p), and distal articulationroll θ. These DOFs allow the orientation and position of the distal tip512 of the catheter 500 to be controlled by the distal articulatingsection 514, then fine-tuned via the proximal articulating section 518.One example of the catheter's utility is the procedure for cannulatingthe renal artery when an occlusion is located at the ostium, as shown inFIG. 27. In this case, the physician would bend the distal articulatingsection 514 to orient the distal tip 512 towards the ostium, whilebending the proximal articulating section 518 to ensure that the distaltip 512 does not contact the occlusion.

The multi-bend algorithm leverages the counteracting pullwire 508′ andthe common mode (uniformly tensioning the remaining three pullwires 508)to independently control the distal articulating section 514 andproximal articulating section 518. In particular, with reference to FIG.28, the multi-bend algorithm that maps articulation commands (α_(d), θ,and α_(p)) to pullwire distances {right arrow over (w)} will bedescribed.

The commanded distal articulations α_(d) and θ are mapped to distalpullwire distances {right arrow over (w)}_(d) through a distalarticulating section solid mechanics model. The three pullwires 508fastened to the control ring 506 are used to produce the desired bend atthe distal articulating section 514. Based on the commanded distalarticulations α_(d) and θ, a bending force is computed using a constantmoment assumption, as disclosed in D. B. Camarillo, C. F. Milne, C. R.Carlson, M. R. Zinn, and J. K. Salisbury; Mechanics Modeling ofTendon-Driven Continuum Manipulators; IEEE Transaction on Robotics,24(6): 1262-1273 (2008). A series spring model of the catheter is thenused to compute the distal pullwire distances {right arrow over (w)}_(d)that will produce the desired moment. However, the computed distalpullwire distances {right arrow over (w)}_(d) may be negative, which isnot physically feasible, since this indicates that the pullwires 508must be pushed. Thus, a null space of control is added to the distalpullwire distances {right arrow over (w)}_(d) until all distal pullwiredistances {right arrow over (w)}_(d) are positive. For the distalarticulating section 514, the null space involves adding the samepullwire distance to all three pullwires 508, which does not modify thedistal articulations α_(d) and θ.

These pullwire distances {right arrow over (w)}_(d) are input to aproximal motion predictor that produces an expected proximalarticulation angle {tilde over (α)}_(p). There are two effects: a distalmoment effect and a common mode effect, that contribute to the expectedproximal articulation angle {tilde over (α)}_(p) based on the pullwiredistances {right arrow over (w)}_(d). With respect to the distal momenteffect, when a distal pullwire is tensioned, a moment is applied at thecontrol ring 506. Based on the constant moment assumption disclosed inD. B. Camarillo, this moment is transferred to the proximal articulatingsection 518. With respect to the common mode effect, when one of thenon-straight pullwires 508 (i.e., spiraled around the transition section516) is tensioned, the path of the pullwire 508 through the transitionsection 516 causes a moment M to be applied to the transition section516 in the direction of the side of the catheter on which the pullwires508 are grouped, as best illustrated in FIG. 29. This moment M causesthe proximal articulating section 518 to bend in the direction of thegrouped pullwires 508. To decouple the proximal and distal bend motionsfrom each other, both of these effects must be taken into account.

The expected proximal articulation angle {tilde over (α)}_(p) due to thedistal moment effect can be computed by applying the material propertiesof the proximal articulating section 518 to the basic moment-bendingrelation:

$\begin{matrix}{{{\overset{\sim}{\alpha}}_{p} = \frac{M_{d} \cdot L_{p}}{K_{p}}},} & \lbrack 2\rbrack\end{matrix}$where M_(d) is the moment applied to the control ring 506, L_(p) is thelength of the proximal articulating section 518, and K_(p) is thebending stiffness of the proximal articulating section 518.

The magnitude of the common mode effect depends upon the path of thenon-straight pullwires 508 through the transition section 516. Tounderstand this effect, it should be noted that the lowest energyconfiguration for a pullwire of a given unloaded length under tensionbetween two points is a straight path. However, the non-straightpullwires have non-zero curvature, and will exert forces on the catheter500 based on the magnitude of the curvature. These forces can beintegrated to calculate an equivalent force and moment that anon-straight pullwire applied to the transition section 516 based onwire tension. Integrating the forces along the wire paths in thetransition section 516 shows that the wire curvatures exert no net forceand a moment proportional to the wire tension. As a result, a puremoment is transferred from the stiff transition section 516 to theflexible proximal articulating section 518, causing a constant-curvatureproximal bend.

The magnitude of this moment M_(t) can be modeled by a gain K_(t) on thewire tension F_(w) in a non-straight pullwire, as follows:M _(t) =K _(t) F _(w)  [3]The gain K_(t) can either be derived from a path integral over thegeometry of a given pullwire, or tuned empirically to experimentallydial in a stiffness or gain. Since the transition section 516 isrelatively rigid, the pullwire geometry in this section does not changeand the gain K_(t) remains constant.

The estimated proximal articulation angle {tilde over (α)}_(p) due tothe common mode effect can be computed by applying the materialproperties of the proximal articulating section 518 to the basicmoment-bending relation:

$\begin{matrix}{{\overset{\sim}{\alpha}}_{p} = \frac{M_{t} \cdot L_{p}}{K_{p}}} & \lbrack 4\rbrack\end{matrix}$The total proximal articulation angle due to the pullwire distances{right arrow over (w)}_(d) can be obtained by combining equations[2]-[4], as follows:

$\begin{matrix}{{\overset{\sim}{\alpha}}_{p} = \frac{\left( {M_{d} + {\sum\limits_{i}{K_{t}^{(i)}F_{w}^{(i)}}}} \right)L_{p}}{K_{p}}} & \lbrack 5\rbrack\end{matrix}$The summation in the numerator of equation [5] operates over alltransition section gains K_(t) ^((i)) and F_(w) ^((i)) corresponding tothe bent pullwires I=1, 2, . . . . The estimated proximal articulationangle {tilde over (α)}_(p) is then subtracted from the commandedproximal articulation α_(p) to produce the amount of additional proximalarticulation angle α_(p) ⁺ required to achieve the command using therelation:α_(p) ⁺=α_(p)−{tilde over (α)}_(p).  [6]

The pullwire distance {right arrow over (w)}_(p) required to achieve theadditional proximal articulation angle α_(p) ⁺ is computed by using aproximal articulating section solid mechanics model. The pullwiredistance {right arrow over (w)}_(p) is different based on the directionof the articulation.

That is, if the additional proximal articulation angle α_(p) ⁺ ispositive (toward the pullwire grouping), then an additional common modeis commanded by tensioning each of the distal pullwires 508 by the samedistance:w _(p) =K _(cm)α_(p) ⁺,  [7]where K_(cm) is a gain that can be set empirically, or can be derivedfrom the transition section gain K_(t) and proximal articulating sectionmaterial properties.

If the additional proximal articulation angle α_(p) ⁺ is negative (awayfrom the pullwire grouping), then the counteracting pullwire 108′ istensioned to achieve the articulation.

The distal pullwire distances {right arrow over (w)}_(d) and proximalpullwire distances {right arrow over (w)}_(p) are summed to produce thefinal set of pullwire distances {right arrow over (w)}.

By achieving independent articulation control over the distalarticulating section 514 and the proximal articulating section 518 usingthe proximal pullwire 108′, greater control when accessing anatomicalsites of interest. For example, the distal pullwire or pullwires 508 inthe direction of the right coronary artery (in this case, pullwire 3)can be tensioned to bend the distal articulating section 514 ninetydegrees to attempt to seat the distal tip 512 within the ostium of theright coronary artery, as illustrated in FIG. 30A. However, the tensionon the distal pullwire(s) 408 will create a moment at the proximalarticulating section 518, and without proper compensation, may cause theproximal articulating section 518 to inadvertently bend in a manner thatpulls the distal tip 512 away from the right coronary artery ostium. Bytensioning the proximal pullwire 508′, the proximal articulating section518 may be bent back towards the right coronary artery ostium toproperly seat the distal tip 512 within the ostium, as illustrated inFIG. 30B. For example, if pullwire 3 is initially tensioned at a forceof 7 units to bend the distal articulating section 514 to create the 90degree bend in the distal articulating section 514, pullwire 4 may betensioned at a force of 9 units to seat the distal tip 512 into theright coronary artery ostium.

Although the catheter 500 has been described as having only onecounteracting pullwire 508′ oriented 180 degrees from the common modepullwires 508 to effect bending of the proximal articulating section 518in only one plane, it should be appreciated that the catheter 500 mayoptionally have two counteracting pullwires 508′. For example, twocounteracting pullwires can be respectively oriented 120 degrees and 240degrees from the common mode pullwires, thereby allowing bending of theproximal articulating section 518 in all planes.

Furthermore, although the catheter 500 has been described as having onlyproximal articulating section 518, the catheter 500 may have multipleproximal articulating sections that have increasing lateral flexibilityfrom the most distal articulating section to the most proximalarticulating section. For example, in the case where a catheter has twoproximal articulating sections, a second transition section similar tothe transition section 516 of the catheter 500 can be incorporatedbetween the two proximal articulating sections. This second transitionsection would transition the counteracting pullwire 508′ to anorientation that is adjacent the common mode pullwires 508, so thatcounteracting pullwire 508′ and remaining three pullwires 508 would bein a common mode within the added proximal articulating section. Thedistal articulating section 514 and first proximal articulating section518 can be independently bent relative to each other in the same manneras described above. However, in this case, applying the same tension onthe counteracting pullwire 508′ as the combined tension on the threeremaining pullwires 508 will bend the additional proximal articulatingsection without bending the first articulating section 518, therebydecoupling the two articulating sections 518 from each other. Anothercounteracting pullwire can be circumferentially disposed 180 degreesfrom the three pullwires 508 and counteracting pullwire 508′ (which areadjacent to each other in the additional proximal articulating section)to bi-directionally bend the additional proximal articulating section inone plane.

As previously discussed above, distal and proximal regions of thecatheters 100, 200, 400, and 500 may be fabricated separately, and thenmounted to each other when the transition section is fabricated. Thereason for fabricating the distal and proximal regions separately isdue, in large part, because the circumferential orientations of thepullwire lumens differ between these proximal and distal regions (i.e.,equally circumferentially spaced from each other in the distal region,and adjacent to each other in the proximal region). To accommodate thedifferent circumferential orientations of the pullwire lumens, the braidmay be incorporated into the catheters using specially designed braidingmachines.

Referring to FIG. 32, one embodiment of a braiding machine 600 capableof braiding three wires 602 (only two shown) having one of twoselectable circumferential orientations to a tube 604 will be described.The braiding machine 600 generally comprises two interchangeable nosecones 606 a, 606 b, a feeder assembly 608, and a braiding assembly 610.

As further shown in FIGS. 33A and 33B, each of the nose cones 606 a, 606b includes a distal tip 614, an external conical surface 616, and acircular tube aperture 618. The nose cone 606 a includes an oblong wireorifice 620 radially outward from coincident with the top of thecircular tube aperture 618 (or alternatively, three circular wireorifices (not shown) separate from the circular tube aperture 618 andspaced closely to each other), and the nose cone 606 includes threecircular wire orifices 622 radially outward and separate from thecircular tube aperture 618 that are equally spaced in an arcuate manner(i.e., one hundred twenty degrees apart) about the circular tubeaperture 618. As will be described in further detail below, the nosecone 606 a can be used to apply braid over a tube 604 with the threewires 602 positioned adjacent to each other, and the nose cone 606 b canbe used to apply braid over a tube 604 with the three wires 602positioned circumferentially equidistant from each other (i.e. 120degrees from each other). The size of the tube aperture 618 ispreferably large enough to just accommodate the tube 604 and any layersthat it may carry, the size of the oblong wire orifice 620 is preferablylarge enough to just accommodate the wires 604 and any layers that theymay carry in a side-by-side relationship, and the sizes of the circularwire orifices 622 are preferably large enough to just accommodate therespective wires 604 and any layers that they may carry.

The feeder assembly 608 is configured for advancing the tube 604 throughthe circular tube aperture 618 and the three wires 602 through theoblong wire orifice 620 or the circular wire orifices 622 at the top ofthe circular tube aperture 618. The feeder assembly 608 may beconventional and include a set of drive rollers 624 distal to the nosecone 606 that pull the tube 604 and wires 602, and a set of tensioningrollers (not shown) proximal to the nose cone 606 that maintain tensionon the tube 604 and wires 602 as they are fed through the nose cone 606.The feeder assembly 608 can be programmed to change the speed at whichthe tube 604 and wires 602 are advanced through the nose cone 606, suchthat the pic count of the braid may be varied.

The braiding assembly 610 is configured for braiding a plurality offilaments 628 around the tube 604 and wires 602 as they are advancedthrough nose cone 606. To this end, the braiding assembly 610 includes aplurality of spindles 630, each of which wraps a respective filament 628around the tube 604 and wires 602. The spindles 630 rotate around eachother and move in and out in a coordinated manner, such that thefilaments 628 form a braid on the tube 604 and wires 602. The braidingassembly 610 and either of the nose cones 606 a, 606 b are arrangedrelative to each other, such that the external surface 616 of therespective nose cone 606 a, 606 b serves as a bearing surface for thefilaments 628 as they are braided around the tube 604 and the wires 602at the distal tip 614 of the nose cone 606 a, 606 b. In the illustratedembodiment, sixteen spindles 630 and corresponding filaments 628 (onlytwo shown) are provided to create the braid, although any number ofspindles 630 and filaments 628 can be used.

As briefly discussed above, the nose cones 606 a, 606 b can beinterchanged with one another to apply braid over tubes 604 and threewires 602 of two different orientations. In particular, the first nosecone 606 a will be installed on the braiding machine 600 whenfabricating a braided assembly having wires 602 that are adjacent toeach other. That is, the oblong wire orifice 620 of the first nose cone606 a will maintain a set of three wires 602 in a closely groupedfashion, such that they remain circumferentially adjacent to each otheras the filaments 628 are braided over a tube 604 and the wires 602. Incontrast, the second nose cone 606 a will be installed on the braidingmachine 600 when fabricating a braided assembly having wires 602 thatcircumferentially equidistant from each other. That is, the threeseparate wire orifices 622 of the second nose cone 606 b will maintainanother set of three wires 602 circumferentially equidistant from eachother (in this case, 120 degrees from each other), such that they remainequidistant from each other as the filaments 628 are braided overanother tube 604 and the wires 602. It should be appreciated thatadditional or alternative nose cones with different numbers of wireorifices or wire orifices of different orientations can be used tofabricate different braided assemblies.

Having described the structure and function of the braiding machine 600,one method of using the braiding machine 600 to fabricate a catheterwill now be described. In this embodiment, the fabricated catheter canbe similar to the catheter 400 described above, with the exception thatthis catheter has three, instead of four, pullwires.

A distal articulating section can be fabricated by first inserting acopper wire process mandrel through a lumen of an inner polymer tube(e.g., a PTFE extrusion) 604 having the intended length of the distalarticulating section. Then, using the braiding machine 600 with thesecond nose cone 606 b, a first layer of braiding is laid down over thelength of the inner polymer tube 604. Notably, this step only requiresthe inner polymer tube to be advanced through the tube aperture 618without advancing any of the three wires 602 through the wire orifices622 of the second nose cone 606 b. Next, the three wires 602 (which takethe form of PTFE-coated stainless steel wire process mandrels) arerespectively disposed over the length of the braided inner polymer tube604 in three equally spaced circumferential positions (i.e., clocked 120degrees from each other), and a second layer of braiding is laid downover the three wires 602. This step requires both the braided innerpolymer tube 604 to be advanced through the tube aperture 618 and thewires 602 to be advanced through the wire orifices 622 of the secondnose cone 606 b during the braiding process. Next, one or more outertubular polymer tubes are laminated over the fully braided inner polymertube. Then, the center copper wire can be pulled from the assembly tocreate a working lumen, and the three stainless steel wires 602 can bepulled from the assembly to respectively create three pullwire lumens.

In a similar manner, a proximal shaft section can be fabricated by firstinserting a copper wire process mandrel the lumen of an inner polymertube (e.g., a PTFE extrusion) 604 having the intended length of theproximal shaft section. Then, using the braiding machine 600 with thefirst nose cone 606 a, a first layer of braiding is laid down over thelength of the inner polymer tube 604. Notably, this step only requiresthe inner polymer tube 604 to be advanced through the tube aperture 618without advancing any of the three wires 602 through the oblong aperture12 of the first nose cone 606 a. Next, the three wires 602 (which takethe form of PTFE-coated stainless steel wire process mandrels withpolyimide tubing) are respectively disposed over the length of thebraided inner polymer tube 604 in adjacent positions, and a second layerof braiding is laid down over the three wires 602. This step requiresboth the braided inner polymer tube 604 to be advanced through the tubeaperture 618 and the wires 602 to be advanced through the oblongaperture of the first nose cone 606 a during the braiding process. Next,one or more outer tubular polymer tubes are laminated over the fullybraided inner polymer tube. Then, the center copper wire can be pulledfrom the assembly to create a working lumen, and the three stainlesssteel wires 602 can be pulled from the assembly to respectively createthree pullwire lumens.

Next, the distal articulating section and the proximal shaft section arecoupled to each other by fabricating a transition section between thedistal articulating section and proximal shaft section and pullwireswith the control ring are installed in the same manner described abovewith respect to fabricating the transition section 416 to couple thedistal articulating section 414 and the combined proximal articulatingsection 418/proximal shaft section 420 together, with the exception thatthree pullwire lumens and corresponding pullwires, instead of fourpullwire lumens and corresponding pullwires, are incorporated into thecatheter.

Referring to FIGS. 34 and 35, another embodiment of a braiding machine700 capable of braiding three wires 602 having two differentcircumferential orientations to a single tube 604 will be described. Thebraiding machine 700 is similar to the previously described braidingmachine 600, with the exception that it is capable of applying the braidto a single tube with different circumferential orientations of thewires 602. In this manner, the wires 602, and thus the pullwire lumens,need not be bonded to any portion of the inner polymer tube. That is,one continuous braid and three continuous wires 602 with varyingcircumferential orientations can be applied over a single tube 604. Inthis manner, not only does this eliminate the processing time requiredto independently fabricate and subsequently join the separate sectionsof the catheter together, it eliminates the inherent variation that mayresult in manually positioning the lumens of the separate cathetersections together. Furthermore, the step of bonding wires to thetransition section that would otherwise be needed to join the distalarticulating section and proximal shaft section together is eliminated.Since the wires must be otherwise weakly bonded to the inner polymertube as a stronger bond would negatively affect the performance of thecompleted catheter, this may be significant, since the braiding processis not gentle and could break or shift the bonds between the wires andthe inner polymer tube.

The braiding machine 700 generally comprises the feeder assembly 608 anda braiding assembly 610, the details of which have been described above.The braiding machine 700 differs from the braiding machine 600 in thatit comprises a single nose cone 706 and an iris assembly 712 (shown inphantom), which in the illustrated embodiment, is installed within thenose cone 706.

Like the previously described nose cones 606 a, 606 b, the nose cone 706includes a distal tip 714, an external conical surface 716, and acircular tube aperture 718. In the illustrated embodiment, the nose cone706 does not include a wire aperture per se. Rather, the size of thetube aperture 718 is preferably large enough to accommodate both thetube 604 and any layers that it may carry, as well as the wires 602 andany layers that they may carry (i.e., the diameter of the tube aperture718 is equal to or slightly greater than the combined diameters of thetube 604 and one of the wires 602). The iris assembly 712 is operable toadjust the relative circumferential positions of the wires 704 as theexit from the tube aperture 718 around the tube 702, and in theillustrated embodiment, between a relative circumferential positionwhere the wires 704 are adjacent to each other in a side-by-siderelationship and a relative circumferential position where the wires 704are positioned circumferentially equidistant from each other (i.e. 120degrees from each other).

To this end, and with reference to FIGS. 36-41, the iris assembly 712comprises three stacked iris plates 720 a, 720 b, and 720 c, each ofwhich includes a center aperture 722, a wire orifice 724 disposedradially outward from the center aperture 722, and at least one arcuatechannel 726 in circumferential alignment with the respective wireorifice 724. The feeder assembly 608 is configured for advancing thetube 604 through the center apertures 722 of the iris assembly 712, aswell as through the tube aperture 718 of the nose cone 706, and the foradvancing the wires 602 through the respective wire orifices 724 of theiris assembly 712, as well as through the periphery of the tube aperture718 of the nose cone 706.

The iris plates 720 are rotatable relative to each other to adjust thecircumferential orientation of the wire orifices 724 relative to eachother, while the arcuate channel(s) 726 of each respective iris plate720 is coincident with the wire orifices 724 of the remaining two irisplates 720. In this manner, any wire orifice 724 may be adjusted viarotation of the respective iris plate 720 without blocking the path ofthe wire orifices 724 of the other iris plates 720. The braidingassembly 610 is configured for braiding the filaments 628 around thetube 604 and the wires 602 as they are fed through the iris assembly 712and as the respective iris plates 720 are rotated relative to each otherto create the braided tube assembly. Thus, the iris assembly 712 may beoperated to circumferentially orient the wires 602 relative to eachother differently along the braided tube assembly.

In the illustrated embodiment, the iris plate 720 a is rotationallyfixed relative to the nose cone 706, while the remaining two iris plates720 b, 720 c are capable of being rotated relative to the nose cone 706.To facilitate their rotation, each of the two iris plates 720 b, 720 cincludes a lever 728 that can be manipulated to rotate the respectiveiris plate 720 b, 720 c. The levers 728 may be manipulated, such thatrotation of the respective iris plates 720 b, 720 c can be synchronouslyautomated with the feeder assembly 608. To accommodate the levers 728,the nose cone 706 may include a slot 730 through which the levers 728for connection to the motor and linkage assembly. To facilitate rotationof the iris plates 720 relative to each other, the iris assembly 712further comprises thrust bearings 730 (shown in phantom in FIG. 36)mounted between the iris plates 720, and in particular, a first thrustbearing 730 a mounted between the respective iris plates 720 a, 720 b, asecond thrust bearing 730 b mounted between the respective iris plates720 b, 720 c, and a third thrust bearing 730 c mounted between the irisplate 720 c and the distal tip 714 of the nose cone 706. Each of thebearings 730 includes a center aperture 732 that accommodates the tube604 and wires 602 as they pass through the iris assembly 712.

Referring back to FIG. 34, the braiding machine 700 further comprises amechanical driver 734 (which may include a motor and appropriatelinkage) connected to the levers 728 for rotating the iris plates 720relative to each other, and a controller 736 configured, while thebraiding assembly 610 is braiding the filaments 628 around the tube 604and the wires 602 over a period of time, instructing the mechanicaldriver 734 to maintain an initial relative rotational orientation of theiris plates 720, such that spacings between the respective wire orifices724 are equal over a first portion of the time period, instructing themechanical driver 734 to gradually change the rotational orientation ofthe iris plates 720, such that spacings between the respective wireorifices 724 decrease over a second portion of the time period until therespective wire orifices 724 are adjacent to each other, and instructingthe mechanical driver 734 to maintain the changed relative rotationalorientation of the iris plates 720, such that the respective wireorifices 724 are adjacent to each other over a third portion of the timeperiod.

As briefly discussed above, the wire orifices 724 and arcuate channel(s)726 of the respective iris plates 720 are arranged in a manner thatallows the three wire orifices 724 to be placed between an adjacentcircumferential orientation and an equally spaced circumferentialorientation without blocking the paths of the wire orifices 724.

To this end, the first iris plate 720 a has two arcuate channels 726 athat straddle the respective wire orifice 724 a (FIG. 40) The furthestextent of each of these arcuate channels 726 a is at least 120 degreesfrom the wire orifice 724 a. The second iris plate 720 b has a singlearcuate channel 720 b with a furthest extent of at least 240 degreescounterclockwise from the wire orifice 724 b of the second iris plate720 b (FIG. 41). The third iris plate 720 c has a single arcuate channel720 c with a furthest extent of at least 120 degrees clockwise from thewire orifice 724 c of the third iris plate 720 c (FIG. 42). It can beappreciated that, when the levers 728 of the respective iris plates 720b, 720 c are moved to their downward position, the wire orifices 724a-724 c are located circumferentially adjacent to each other, as shownin FIG. 38. In contrast, when the levers 728 of the respective irisplates 720 b, 720 c are moved to their upward position, the wireorifices 724 a-724 c are circumferentially spaced equidistant from eachother, as shown in FIG. 39.

The right arcuate channel 726 a of the first iris plate 720 a remainscoincident with the wire orifice 724 b of the second iris plate 720 b asthe lever 728 of the second iris plate 720 b is moved between the upwardand downward positions. Thus, the right arcuate channel 726 a preventsthe first iris plate 720 a from blocking the path of the wire orifice724 b of the second iris plate 720 b. Similarly, the left arcuatechannel 726 a of the first iris plate 720 a remains coincident with thewire orifice 724 c of the third iris plate 720 c as the lever 728 of thethird iris plate 720 c is moved between the upward and downwardpositions. Thus, the left arcuate channel 726 a prevents the first irisplate 720 a from blocking the path of the wire orifice 724 c of thethird iris plate 720 c.

The arcuate channel 726 b of the second iris plate 720 b remainscoincident with the wire orifice 724 a of the first iris plate 720 a andthe wire orifice 724 c of the third iris plate 720 c as the lever 728 ofthe second iris plate 720 b is moved between the upward and downwardpositions. Thus, the arcuate channel 726 b prevents the second irisplate 720 b from blocking the paths of the wire orifice 724 a of thefirst iris plate 720 a and the wire orifice 724 c of the third irisplate 720 c. The arcuate channel 726 c of the third iris plate 720 cremains coincident with the wire orifice 724 a of the first iris plate720 a and the wire orifice 724 b of the second iris plate 720 b as thelever 728 of the third iris plate 720 c is moved between the upward anddownward positions. Thus, the arcuate channel 726 c prevents the thirdiris plate 720 c from blocking the paths of the wire orifice 724 a ofthe first iris plate 720 a and the wire orifice 724 b of the second irisplate 720 b.

Having described the structure and function of the braiding machine 700,one method of using the braiding machine 700 to fabricate a catheterwill now be described. The catheter can be fabricated by first insertinga copper wire process mandrel through a lumen of an inner polymer tube(e.g., a PTFE extrusion) having the intended length of the catheter.Then, a first layer of braiding is laid down over the length of theinner polymer tube. Notably, this step only requires the inner polymertube to be advanced through the center aperture 722 of the iris assembly712 and the tube aperture 718 of the nose cone 706 without advancing anyof the three wires 602 through the wire orifices 724 of the irisassembly 712 or the tube aperture 718 of the nose cone 706. Next, thethree wires 602 (which take the form of PTFE-coated stainless steel wireprocess mandrels) are respectively disposed over the length of thebraided inner polymer tube in varying circumferential positions, and asecond layer of braiding is laid down over the three wires 602.

This step requires both the braided inner polymer tube to be advancedthrough the center aperture 722 of the iris assembly 712 and the tubeaperture 618 of the nose cone 706, and the wires 602 to be advancedthrough the wire orifices 724 of the iris assembly 712 and the tubeaperture 718 of the nose cone 706 during the braiding process.Furthermore, during this step, the levers 728 of the iris plates 720 b,720 c are manipulated to change the relative circumferential positionsof the wire orifices 724 of the iris assembly 712, and thus, the wires602 on which the braid is laid. In particular, during the length of thedistal articulating section of the catheter, the levers 728 of therespective iris plates 720 b, 720 c are moved to their downwardposition, such that the wire orifices 724 a-724 c, and thus, the wires602, are located circumferentially adjacent to each other. During thelength of the transition section of the catheter, the levers 728 of therespective iris plates 720 b, 720 c are gradually moved to their upwardposition, such that the wire orifices 724 a-724 c, and thus, the wires602, are gradually moved from a position where they arecircumferentially adjacent to each other at the distal-most extent ofthe transition section to a position where they are circumferentiallyspaced equidistant from each other at the proximal-most extent of thetransition section. During the length of the proximal shaft section ofthe catheter, the levers 728 of the respective iris plates 720 b, 720 care maintained in their upward position, such that the spacings of thewire orifices 724 a-724 c, and thus, the wires 602, is maintainedcircumferentially equidistant from each other. Next, one or more outertubular polymer tubes are laminated over the fully braided inner polymertube. Then, the center copper wire can be pulled from the assembly tocreate a working lumen, and the three stainless steel wires 602 can bepulled from the assembly to respectively create three pullwire lumens.

Although the iris assembly has been described as comprising three irisplates for respectively accommodating three wires 602, it should beappreciated that the number of iris plates can be less or more thanthree, depending on the number of wires 602 that are to be incorporatedinto the catheter.

For example, in the case where two wires 602 are to be accommodated, theiris assembly may comprise only two iris plates. In this case, one ofthe iris plates will have a single arcuate channel with a furthestextent at least 180 degrees clockwise from the wire orifice, and theother iris plate will have a single arcuate channel with a furthestextent at least 180 degrees counterclockwise from the wire orifice.Thus, the wire orifices in this iris assembly may be selectively locatedcircumferentially adjacent to each other or circumferentially spacedequidistant from each other by 180 degrees.

In the case where four wires 602 are to be accommodated, the irisassembly may comprise four iris plates. In this case, the first irisplate has a single arcuate channel that extends virtually all the wayaround the respective iris plate from one side of the wire orifice tothe other side of the wire orifice. The second iris plate has a singlearcuate channel with a furthest extent of at least 270 degreescounterclockwise from the wire orifice of the second iris plate. Thethird iris plate has a single arcuate channel with a furthest extent ofat least 270 degrees clockwise from the wire orifice of the third irisplate. The fourth iris plate has a single arcuate channel that extendsvirtually all the way around the respective iris plate from one side ofthe wire orifice to the other side of the wire orifice. Thus, the wireorifices in this iris assembly may be selectively locatedcircumferentially adjacent to each other or circumferentially spacedequidistant from each other by 90 degrees.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed is:
 1. A steerable catheter, comprising: a flexible catheter body including a proximal shaft section, a transition section, and a distal articulating section; a proximal steering interface coupled to the proximal shaft section; at least one hollow axially stiffening member extending through the proximal shaft section, the at least one stiffening member being laterally offset from a geometric cross-sectional center of the proximal shaft section; a plurality of lumens extending through the transition section and the distal articulating section; and a plurality of pullwires extending through the at least one hollow stiffening member in the proximal shaft section, each pullwire further extending through a respective lumen in the transition section into the distal articulating section, each of the pullwires having a distal end that terminates in the catheter body distal to the distal articulating section and a proximal end that terminates in the proximal steering interface, wherein the proximal steering interface is manipulatable to selectively tension one or more pullwires of the plurality to bend the distal articulating section.
 2. The steerable catheter of claim 1, wherein the at least one stiffening member comprises a single stiffening member through which the plurality of pullwires extend.
 3. The steerable catheter of claim 1, wherein the plurality of pullwires comprises at least three pullwires.
 4. The steerable catheter of claim 1, wherein the plurality of lumens are circumferentially spaced within the distal articulating section.
 5. The steerable catheter of claim 1, wherein the cross-sectional shape of the catheter body is either circular or rectangular.
 6. The steerable catheter of claim 1, wherein each of the plurality of lumens is an unsupported lumen.
 7. The steerable catheter of claim 4, wherein the plurality of lumens are equally circumferentially spaced from each other.
 8. The steerable catheter of claim 1, wherein the plurality of lumens are spiraled within the transition section.
 9. The steerable catheter of claim 1, wherein the transition body section is more rigid than the distal articulating section, such that when any of the plurality of pullwires is selectively tensioned, a resulting compressive force on the catheter body causes the distal articulating section to bend relative to the transition section.
 10. The steerable catheter of claim 1, further comprising a control ring disposed within the catheter body distal to the distal articulating section, wherein the plurality of pullwires is connected to the control ring.
 11. A robotically controlled catheter system, comprising: the steerable catheter of claim 1; a drive assembly coupled to the proximal steering interface of the steerable catheter; and a master controller including a user interface configured for being manipulated to actuate the drive assembly, thereby selectively tensioning the plurality of pullwires to bend the distal articulating section.
 12. The steerable catheter of claim 1, further comprising a guidewire lumen extending through the distal articulating section.
 13. The steerable catheter of claim 12, further comprising a rapid exchange port in communication with the guidewire lumen, wherein the rapid exchange port is distal to the proximal shaft section.
 14. The steerable catheter of claim 13, wherein the at least one stiffening member forms the proximal shaft section.
 15. The steerable catheter of claim 1, further comprising an adapter mounted within the transition section, the adapter having a distal end that interfaces with the plurality of lumens, and a proximal end that interfaces with the at least one stiffening tube, the adapter further having a plurality of channels formed in an external surface of the adapter, the plurality of pullwires being disposed with the respective plurality of channels.
 16. The steerable catheter of claim 15, wherein the at least one stiffening member comprises a single stiffening member through which the plurality of pullwires extend, the distal end of the adapter has a plurality of lumens in respective communication with the plurality of lumens in the distal articulating section, the proximal end of the adapter has a single port in communication with the stiffening tube, and the plurality of pullwires respectively extend through the plurality of lumens of the adapter, along the channels formed in the external surface of the adapter, and into the single port of the adapter.
 17. The steerable catheter of claim 16, wherein at least one of the channels is spiraled around the external surface of the adapter.
 18. The steerable catheter of claim 1, wherein the at least one stiffening member comprises a plurality of stiffening members through which the plurality of pullwires respectively extend.
 19. The steerable catheter of claim 18, wherein the plurality of stiffening members are grouped in a manner that locates a centers of each stiffening member within an arcuate angle of less than one hundred eighty degrees relative to the geometric cross-sectional center of the proximal shaft section.
 20. The steerable catheter of claim 19, wherein the arcuate angle is less than ninety degrees.
 21. The steerable catheter of claim 19, wherein the arcuate angle is less than forty-five degrees.
 22. The steerable catheter of claim 1, wherein the catheter body has a neutral axis, and wherein each of the pullwires is located relative to the neutral axis in the proximal shaft section a first distance, and located relative to the neutral axis in the distal articulating section a second distance, thereby defining the extent to which each of the proximal shaft section and the distal articulating section articulates when the respective pullwires are tensioned.
 23. The steerable catheter of claim 22, wherein the second distance is greater than the first distance, such that the distal articulating section articulates independent of the relative bending stiffness between the proximal shaft section and the distal articulating section when the each pullwire is tensioned.
 24. The steerable catheter of claim 22, wherein the proximal shaft section has a first bending stiffness, and the distal articulating section has a second bending stiffness, thereby further defining the extent to which each of the proximal shaft section and the distal articulating section articulates when the each pullwire is tensioned.
 25. The steerable catheter of claim 24, wherein the second distance is greater than the first distance, and the first bending stiffness is greater than the second bending stiffness.
 26. The steerable catheter of claim 1, wherein the catheter body includes a proximal articulating section between the proximal shaft section and the transition section, the plurality of lumens are equally circumferentially spaced from each other, such that when all of the pullwires are uniformly tensioned, the resulting compressive force on the catheter body causes the proximal articulating section to bend relative to the proximal shaft section without bending the distal articulating section relative to the transition section.
 27. The steerable catheter of claim 26, wherein the proximal articulating section is more rigid than the distal articulating section, such that when only one of the pullwires is tensioned, the resulting compressive force on the catheter body causes the distal articulating section to bend relative to the transition section more than the proximal articulating section bends relative to the proximal shaft section.
 28. The steerable catheter of claim 26, further comprising: a lumen extending through the proximal articulating section; and a counteracting pullwire extending through the lumen in the proximal articulating section, the counteracting pullwire having a distal end terminating in the transition section and a proximal end that terminates in the proximal steering interface, wherein the proximal steering interface is further manipulatable to tension the counteracting pullwire to provide a compressive force on the catheter body that opposes the compressive force provided by the plurality of pullwires when tensioned.
 29. The steerable catheter of claim 28, wherein the counteracting pullwire is circumferentially disposed 180 degrees from a common mode of the plurality of pullwires in the proximal articulating section.
 30. The steerable catheter of claim 28, further comprising: another lumen extending through the proximal articulating section; and another counteracting pullwire extending through the other lumen in the proximal articulating section, the other counteracting pullwire having a distal end terminating in the transition section and a proximal end that terminates in the proximal steering interface, wherein the proximal steering interface is further manipulatable to tension the other counteracting pullwire to provide a compressive force on the catheter body that opposes the compressive force provided by the plurality of pullwires when tensioned.
 31. The steerable catheter of claim 30, wherein the counteracting pullwires are respectively circumferentially disposed 120 degrees and 240 degrees from a common mode of the plurality of pullwires in the proximal articulating section.
 32. A robotically controlled catheter system, comprising: the steerable catheter of claim 28; a drive assembly coupled to the proximal steering interface of the steerable catheter; a master controller including a user interface configured for being manipulated to actuate the drive assembly, thereby selectively tensioning the plurality of pullwires and the counteracting pullwire; and a processor configured for receiving an input from the user interface defining a distal articulation angle and a distal articulation roll of the distal articulating section of the steering catheter, and further defining a proximal articulation angle of the proximal articulating section, determining which of the pullwires to be displaced and the respective distances that the pullwires should be displaced to achieve the defined distal articulation angle and distal articulation roll of the distal body section of the steering catheter, predicting a proximal articulation angle of the proximal articulating section solely caused by a moment applied to the distal articulating section and a moment applied to the transition section by the displacement of the pullwires, computing a difference between the predicted proximal articulation angle and the defined proximal articulation angle to obtain a corrected proximal articulation angle, and determining an additional distance that at least one of the plurality of pullwires and the counteracting pullwire should be displaced to further achieve the corrected proximal articulation angle.
 33. The robotically controlled catheter system of claim 32, wherein the plurality of lumens are equally circumferentially spaced from each other, and the at least one of the plurality of pullwires and the counteracting pullwire comprises the plurality of pullwires.
 34. A steerable catheter, comprising: a flexible catheter body including a proximal shaft section and a distal articulating section; a proximal steering interface coupled to the proximal shaft section; one or more hollow axially stiffening members extending through the proximal shaft section, the one or more stiffening members being laterally offset from, and disposed asymmetrically with respect to, a geometric cross-sectional center of the proximal shaft section so as to shift a neutral axis of the proximal shaft section away from said geometric cross-sectional center of the proximal shaft section; a plurality of lumens extending through the distal articulating section; and a plurality of pullwires extending through the one or more stiffening members in the proximal shaft section, each pullwire of the plurality further extending through a respective lumen of the distal articulating section, each of the pullwires having a distal end that terminates in the catheter body distal to the distal articulating section and a proximal end that terminates in the proximal steering interface, wherein the proximal steering interface is manipulatable to selectively tension one or more pullwires of the plurality to bend the distal articulating section.
 35. The steerable catheter of claim 34, wherein the one or more stiffening members comprises a plurality of stiffening members grouped in a manner that locates a center of each stiffening member within an arcuate angle of less than one hundred eighty degrees relative to the geometric cross-sectional center of the proximal shaft section.
 36. The steerable catheter of claim 34, wherein each of the pullwires is located relative to the neutral axis in the proximal shaft section a first distance, and located relative to a neutral axis of the distal articulating section a second distance, thereby defining the extent to which each of the proximal shaft section and the distal articulating section articulates when the respective pullwires are tensioned.
 37. The steerable catheter of claim 34, wherein the plurality of lumens are circumferentially spaced in the distal articulating section.
 38. A robotically controlled catheter system, comprising: the steerable catheter of claim 34; a drive assembly coupled to the proximal steering interface of the steerable catheter; and a master controller including a user interface configured for being manipulated to actuate the drive assembly, thereby selectively tensioning pullwires of the plurality of pullwires to bend the distal articulating section.
 39. The steerable catheter of claim 34, wherein the catheter body includes a transition section between the proximal shaft section and the distal articulating section, and a proximal articulating section between the proximal shaft section and the transition section, the plurality of lumens being equally circumferentially spaced from each other, such that when all of the pullwires are uniformly tensioned, the resulting compressive force on the catheter body causes the proximal articulating section to bend relative to the proximal shaft section without bending the distal articulating section relative to the transition section.
 40. The steerable catheter of claim 39, further comprising: a first further lumen extending through the proximal articulating section; and a first counteracting pullwire extending through the first further lumen in the proximal articulating section, the first counteracting pullwire having a distal end terminating in the transition section and a proximal end that terminating in the proximal steering interface, wherein the proximal steering interface is further manipulatable to tension the first counteracting pullwire to provide a compressive force on the catheter body that opposes a compressive force provided by tensioning pullwires of the plurality of pullwires.
 41. The steerable catheter of claim 40, further comprising: a second further lumen extending through the proximal articulating section; and a second counteracting pullwire extending through the second further lumen in the proximal articulating section, the second counteracting pullwire having a distal end terminating in the transition section and a proximal end terminating in the proximal steering interface, wherein the proximal steering interface is further manipulatable to tension the second counteracting pullwire to provide a compressive force on the catheter body that opposes the compressive force provided by tensioning pullwires of the plurality of pullwires. 